feat: bulk delete + merge activities in feed

- Select mode in ActivityFeed: toggle with Select button (logged-in only),
  cards become clickable with checkmark indicator, action bar fixed at bottom
- Bulk delete: calls existing DELETE /api/activity/{id} for each selected,
  removes from local feed state immediately
- Bulk merge: POST /api/merge sorts by started_at (earliest = primary),
  sums distance/duration/elevation, weighted-averages HR/power, concatenates
  geojson and timeseries; backs up originals to _merge_backup/ for recovery
- GET /api/merges returns per-user hidden list; feed filters secondaries
  client-side on load so static shards don't need a rebuild to hide them
- POST /api/unmerge/{id} restores primary from backup, unhides secondaries
- ActivityDetail: shows "Merged (N)" badge + Unmerge button for owners
- Fix: edit button now works from personal profile feed (handle was missing
  from year-shard activities; injected from filterHandle on sessionStorage write)

bincio/serve/routers/merge.py

@@ -0,0 +1,270 @@
+"""Merge and unmerge activity endpoints."""
+from __future__ import annotations
+
+import json
+import shutil
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException
+from fastapi.responses import JSONResponse
+from pydantic import BaseModel
+
+from bincio.serve import deps, tasks
+from bincio.serve.db import User
+
+router = APIRouter()
+
+_MERGES_FILE = "_merges.json"
+_BACKUP_DIR = "_merge_backup"
+
+
+def _read_merges(user_dir: Path) -> dict:
+    p = user_dir / _MERGES_FILE
+    if p.exists():
+        try:
+            return json.loads(p.read_text(encoding="utf-8"))
+        except (OSError, json.JSONDecodeError):
+            pass
+    return {"hidden": [], "merges": {}}
+
+
+def _write_merges(user_dir: Path, data: dict) -> None:
+    (user_dir / _MERGES_FILE).write_text(
+        json.dumps(data, ensure_ascii=False), encoding="utf-8"
+    )
+
+
+def _now_iso() -> str:
+    return datetime.now(timezone.utc).isoformat()
+
+
+@router.get("/api/merges")
+async def get_merges(user: User = Depends(deps._require_auth)) -> JSONResponse:
+    user_dir = deps._get_data_dir() / user.handle
+    return JSONResponse(_read_merges(user_dir))
+
+
+class MergeRequest(BaseModel):
+    activity_ids: list[str]
+
+
+@router.post("/api/merge")
+async def merge_activities(
+    body: MergeRequest,
+    user: User = Depends(deps._require_auth),
+) -> JSONResponse:
+    if len(body.activity_ids) < 2:
+        raise HTTPException(400, "Need at least 2 activities to merge")
+
+    dd = deps._get_data_dir()
+    user_dir = dd / user.handle
+    acts_dir = user_dir / "activities"
+
+    activities: list[dict] = []
+    for aid in body.activity_ids:
+        deps._check_id(aid)
+        p = acts_dir / f"{aid}.json"
+        if not p.exists():
+            raise HTTPException(404, f"Activity {aid} not found")
+        try:
+            a = json.loads(p.read_text(encoding="utf-8"))
+        except (OSError, json.JSONDecodeError):
+            raise HTTPException(500, f"Could not read activity {aid}")
+        a["_id"] = aid
+        activities.append(a)
+
+    sports = {a.get("sport") for a in activities}
+    if len(sports) > 1:
+        raise HTTPException(400, "Cannot merge activities of different sports")
+
+    activities.sort(key=lambda a: a.get("started_at", ""))
+    primary = activities[0]
+    secondaries = activities[1:]
+    primary_id = primary["_id"]
+    secondary_ids = [a["_id"] for a in secondaries]
+
+    def _sum(key: str) -> float | None:
+        vals = [a.get(key) for a in activities if a.get(key) is not None]
+        return sum(vals) if vals else None
+
+    def _wavg(key: str) -> float | None:
+        pairs = [(a.get(key), a.get("moving_time_s")) for a in activities]
+        pairs = [(v, w) for v, w in pairs if v is not None and w and w > 0]
+        if not pairs:
+            return None
+        total_w = sum(w for _, w in pairs)
+        return sum(v * w for v, w in pairs) / total_w if total_w > 0 else None
+
+    distance_m = _sum("distance_m")
+    duration_s = _sum("duration_s")
+    moving_time_s = _sum("moving_time_s")
+    elevation_gain_m = _sum("elevation_gain_m")
+    avg_speed_kmh = (distance_m / moving_time_s * 3.6) if distance_m and moving_time_s else None
+    avg_hr_bpm_val = _wavg("avg_hr_bpm")
+    avg_power_w_val = _wavg("avg_power_w")
+
+    backup_dir = user_dir / _BACKUP_DIR
+    backup_dir.mkdir(exist_ok=True)
+    for suffix in (".json", ".geojson", ".timeseries.json"):
+        src = acts_dir / f"{primary_id}{suffix}"
+        if src.exists():
+            shutil.copy2(src, backup_dir / f"{primary_id}{suffix}.bak")
+
+    primary_data: dict[str, Any] = {k: v for k, v in primary.items() if not k.startswith("_")}
+    primary_data["distance_m"] = distance_m
+    primary_data["duration_s"] = duration_s
+    primary_data["moving_time_s"] = moving_time_s
+    primary_data["elevation_gain_m"] = elevation_gain_m
+    if avg_speed_kmh is not None:
+        primary_data["avg_speed_kmh"] = round(avg_speed_kmh, 3)
+    if avg_hr_bpm_val is not None:
+        primary_data["avg_hr_bpm"] = round(avg_hr_bpm_val)
+    if avg_power_w_val is not None:
+        primary_data["avg_power_w"] = round(avg_power_w_val)
+    primary_data["merged_ids"] = secondary_ids
+
+    (acts_dir / f"{primary_id}.json").write_text(
+        json.dumps(primary_data, ensure_ascii=False, indent=2), encoding="utf-8"
+    )
+
+    _merge_geojson(acts_dir, primary_id, secondary_ids)
+    _merge_timeseries(acts_dir, primary_id, secondary_ids, activities)
+
+    merges = _read_merges(user_dir)
+    for sid in secondary_ids:
+        if sid not in merges["hidden"]:
+            merges["hidden"].append(sid)
+    merges.setdefault("merges", {})[primary_id] = {
+        "secondary_ids": secondary_ids,
+        "merged_at": _now_iso(),
+    }
+    _write_merges(user_dir, merges)
+
+    from bincio.render.merge import merge_one
+    merge_one(user_dir, primary_id)
+    tasks._trigger_rebuild(user.handle)
+
+    return JSONResponse({"ok": True, "primary_id": primary_id, "hidden": secondary_ids})
+
+
+@router.post("/api/unmerge/{primary_id}")
+async def unmerge_activity(
+    primary_id: str,
+    user: User = Depends(deps._require_auth),
+) -> JSONResponse:
+    deps._check_id(primary_id)
+    dd = deps._get_data_dir()
+    user_dir = dd / user.handle
+    acts_dir = user_dir / "activities"
+    backup_dir = user_dir / _BACKUP_DIR
+
+    merges = _read_merges(user_dir)
+    merge_info = merges.get("merges", {}).get(primary_id)
+    if not merge_info:
+        raise HTTPException(404, "No merge record found for this activity")
+
+    secondary_ids: list[str] = merge_info.get("secondary_ids", [])
+
+    for suffix in (".json", ".geojson", ".timeseries.json"):
+        bak = backup_dir / f"{primary_id}{suffix}.bak"
+        if bak.exists():
+            shutil.copy2(bak, acts_dir / f"{primary_id}{suffix}")
+            bak.unlink()
+
+    merges["hidden"] = [h for h in merges.get("hidden", []) if h not in secondary_ids]
+    merges["merges"].pop(primary_id, None)
+    _write_merges(user_dir, merges)
+
+    from bincio.render.merge import merge_one
+    merge_one(user_dir, primary_id)
+    tasks._trigger_rebuild(user.handle)
+
+    return JSONResponse({"ok": True, "restored": secondary_ids})
+
+
+def _merge_geojson(acts_dir: Path, primary_id: str, secondary_ids: list[str]) -> None:
+    primary_path = acts_dir / f"{primary_id}.geojson"
+    if not primary_path.exists():
+        return
+    try:
+        geo = json.loads(primary_path.read_text(encoding="utf-8"))
+    except (OSError, json.JSONDecodeError):
+        return
+    features: list = list(geo.get("features", []))
+    for sid in secondary_ids:
+        p = acts_dir / f"{sid}.geojson"
+        if not p.exists():
+            continue
+        try:
+            sec = json.loads(p.read_text(encoding="utf-8"))
+            features.extend(sec.get("features", []))
+        except (OSError, json.JSONDecodeError):
+            continue
+    geo["features"] = features
+    primary_path.write_text(json.dumps(geo, ensure_ascii=False), encoding="utf-8")
+
+
+def _merge_timeseries(
+    acts_dir: Path,
+    primary_id: str,
+    secondary_ids: list[str],
+    activities: list[dict],
+) -> None:
+    primary_path = acts_dir / f"{primary_id}.timeseries.json"
+    if not primary_path.exists():
+        return
+    try:
+        merged = json.loads(primary_path.read_text(encoding="utf-8"))
+    except (OSError, json.JSONDecodeError):
+        return
+
+    merged = {k: list(v) if isinstance(v, list) else v for k, v in merged.items()}
+
+    _ARRAY_KEYS = ("lat", "lon", "elevation_m", "speed_kmh", "hr_bpm", "cadence_rpm", "power_w", "temperature_c")
+
+    for i, sid in enumerate(secondary_ids):
+        sec_path = acts_dir / f"{sid}.timeseries.json"
+        if not sec_path.exists():
+            continue
+        try:
+            sec = json.loads(sec_path.read_text(encoding="utf-8"))
+        except (OSError, json.JSONDecodeError):
+            continue
+
+        sec_t: list = sec.get("t") or []
+        if not sec_t:
+            continue
+
+        try:
+            p_start = datetime.fromisoformat(
+                activities[0].get("started_at", "").replace("Z", "+00:00")
+            ).timestamp()
+            s_start = datetime.fromisoformat(
+                activities[i + 1].get("started_at", "").replace("Z", "+00:00")
+            ).timestamp()
+            offset = s_start - p_start
+        except (ValueError, TypeError):
+            cur_t: list = merged.get("t") or []
+            offset = (cur_t[-1] + 1) if cur_t else 0
+
+        adjusted_t = [offset + t for t in sec_t]
+        primary_len = len(merged.get("t") or [])
+
+        if merged.get("t") is None:
+            merged["t"] = []
+        merged["t"].extend(adjusted_t)
+
+        for key in _ARRAY_KEYS:
+            sec_vals = sec.get(key)
+            if sec_vals is None:
+                if merged.get(key) is not None:
+                    merged[key] = merged[key] + [None] * len(sec_t)
+            else:
+                if merged.get(key) is None:
+                    merged[key] = [None] * primary_len + list(sec_vals)
+                else:
+                    merged[key] = merged[key] + list(sec_vals)
+
+    primary_path.write_text(json.dumps(merged, ensure_ascii=False), encoding="utf-8")

bincio/serve/server.py

@@ -20,12 +20,14 @@ from bincio.serve.routers import (
     activities,
     admin,
     auth,
+    budget,
     download,
     feed,
     garmin,
     gear,
     ideas,
     me,
+    merge,
     ogimage,
     segments,
     strava,
@@ -63,6 +65,8 @@ for _router in [
     me.router,
     admin.router,
     activities.router,
+    merge.router,
+    budget.router,
     download.router,
     uploads.router,
     segments.router,

site/src/components/ActivityDetail.svelte

@@ -36,6 +36,25 @@
     pr_elapsed_s: number;
   }
   let segmentEfforts: SegmentEffortHit[] = [];
+  let unmergeWorking = false;
+
+  async function _unmerge() {
+    if (!confirm('Unmerge this activity? The original tracks will be restored and the secondary activities will reappear in your feed.')) return;
+    unmergeWorking = true;
+    try {
+      const r = await fetch(`/api/unmerge/${activity.id}`, { method: 'POST', credentials: 'include' });
+      if (r.ok) {
+        window.location.reload();
+      } else {
+        const d = await r.json();
+        alert(d.detail ?? 'Unmerge failed');
+      }
+    } catch {
+      alert('Unmerge failed');
+    } finally {
+      unmergeWorking = false;
+    }
+  }
 
   // Local overrides applied immediately after a save (no re-fetch needed)
   let localTitle = '';
@@ -381,6 +400,20 @@
           class="text-xs px-2 py-0.5 rounded border border-zinc-700 text-zinc-400 hover:border-zinc-500 hover:text-white transition-colors shrink-0"
         >+ segment</a>
       {/if}
+      {#if detail?.merged_ids?.length}
+        <span class="text-xs px-2 py-0.5 rounded border border-zinc-600 text-zinc-400 shrink-0">
+          Merged ({detail.merged_ids.length})
+        </span>
+        {#if editEnabled}
+          <button
+            class="text-xs px-2 py-0.5 rounded border border-zinc-700 text-zinc-400 hover:border-zinc-500 hover:text-white transition-colors shrink-0 disabled:opacity-40"
+            disabled={unmergeWorking}
+            on:click={_unmerge}
+          >
+            {unmergeWorking ? 'Working…' : 'Unmerge'}
+          </button>
+        {/if}
+      {/if}
     </div>
     {#if descriptionHtml}
       <div class="text-zinc-400 mt-2 text-sm leading-relaxed [&_img]:rounded-lg [&_img]:my-2 [&_p]:my-1 [&_a]:text-blue-400">

site/src/components/ActivityFeed.svelte

@@ -59,6 +59,73 @@
   /** Logged-in handle — resolved async via bincio:me event. */
   let me: string = '';
 
+  // ── Bulk / select mode ────────────────────────────────────────────────────
+  let selectMode = false;
+  let selected: Set<string> = new Set();
+  let hiddenIds: Set<string> = new Set();
+  let bulkWorking = false;
+
+  async function _loadMerges() {
+    try {
+      const r = await fetch('/api/merges', { credentials: 'include' });
+      if (r.ok) {
+        const data = await r.json();
+        hiddenIds = new Set(data.hidden ?? []);
+      }
+    } catch { /* non-critical */ }
+  }
+
+  function _toggleSelect(id: string) {
+    const s = new Set(selected);
+    s.has(id) ? s.delete(id) : s.add(id);
+    selected = s;
+  }
+
+  function _exitSelect() {
+    selectMode = false;
+    selected = new Set();
+  }
+
+  async function _deleteSelected() {
+    const ids = [...selected];
+    if (!confirm(`Delete ${ids.length} activit${ids.length === 1 ? 'y' : 'ies'}? This cannot be undone.`)) return;
+    bulkWorking = true;
+    for (const id of ids) {
+      try {
+        const r = await fetch(`/api/activity/${id}`, { method: 'DELETE', credentials: 'include' });
+        if (r.ok) all = all.filter(a => a.id !== id);
+      } catch { /* continue */ }
+    }
+    bulkWorking = false;
+    _exitSelect();
+  }
+
+  async function _mergeSelected() {
+    const ids = [...selected];
+    if (ids.length < 2) return;
+    bulkWorking = true;
+    try {
+      const r = await fetch('/api/merge', {
+        method: 'POST',
+        credentials: 'include',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ activity_ids: ids }),
+      });
+      const data = await r.json();
+      if (r.ok) {
+        for (const hid of data.hidden ?? []) hiddenIds.add(hid);
+        hiddenIds = new Set(hiddenIds);
+        _exitSelect();
+      } else {
+        alert(data.detail ?? 'Merge failed');
+      }
+    } catch {
+      alert('Merge failed');
+    } finally {
+      bulkWorking = false;
+    }
+  }
+
   function computeDateRange(preset: string): { dateFrom: string; dateTo: string } {
     if (preset === 'all') return { dateFrom: '', dateTo: '' };
     if (/^\d{4}$/.test(preset)) {
@@ -74,11 +141,14 @@
     return { dateFrom: `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}T`, dateTo: '' };
   }
 
+  // Filter out secondary activities hidden by a merge.
+  $: withMerge = all.filter(a => !hiddenIds.has(a.id));
+
   // Show private activities only to their owner.
   // On a profile page (filterHandle set): show unlisted if me === filterHandle.
   // On the global feed: show unlisted only for the logged-in user's own activities.
   $: isOwner = filterHandle !== '' && me === filterHandle;
-  $: withPrivacy = all.filter(a => {
+  $: withPrivacy = withMerge.filter(a => {
     if (isUnlisted(a.privacy)) {
       return filterHandle ? isOwner : (me !== '' && (a as any).handle === me);
     }
@@ -196,8 +266,12 @@
     // Resolve the logged-in handle so we can show the owner their private activities.
     if ((window as any).__bincioMe !== undefined) {
       me = (window as any).__bincioMe;
+      _loadMerges();
     } else {
-      window.addEventListener('bincio:me', (e: Event) => { me = (e as CustomEvent).detail; }, { once: true });
+      window.addEventListener('bincio:me', (e: Event) => {
+        me = (e as CustomEvent).detail;
+        _loadMerges();
+      }, { once: true });
     }
 
     try {
@@ -287,6 +361,17 @@
         on:click={() => viewMode = 'map'}
       >Map</button>
     </div>
+    {#if me}
+      <button
+        class="px-3 py-2 rounded-lg border text-sm transition-colors shrink-0"
+        class:border-zinc-700={!selectMode}
+        class:text-zinc-400={!selectMode}
+        class:border-[--accent]={selectMode}
+        class:text-white={selectMode}
+        style={selectMode ? 'background:var(--accent-dim)' : ''}
+        on:click={() => { if (selectMode) _exitSelect(); else selectMode = true; }}
+      >{selectMode ? 'Cancel' : 'Select'}</button>
+    {/if}
   </div>
 </div>
 
@@ -368,8 +453,15 @@
 {:else}
   <div class="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4">
     {#each visible as a (a.id)}
+      {@const isSelected = selected.has(a.id)}
       <!-- relative + isolate so the stretched activity link stays below the handle link -->
-      <div class="relative rounded-xl bg-zinc-900 border border-zinc-800 p-4 hover:border-zinc-600 hover:bg-zinc-800/80 transition-all group">
+      <!-- svelte-ignore a11y-click-events-have-key-events -->
+      <!-- svelte-ignore a11y-no-static-element-interactions -->
+      <div
+        class="relative rounded-xl bg-zinc-900 border p-4 transition-all group {isSelected ? 'border-[--accent]' : 'border-zinc-800'} {selectMode ? 'cursor-pointer' : 'hover:border-zinc-600 hover:bg-zinc-800/80'}"
+        style={isSelected ? 'background:var(--accent-dim)' : ''}
+        on:click={selectMode ? () => _toggleSelect(a.id) : undefined}
+      >
         <!-- header -->
         <div class="flex items-start justify-between gap-2 mb-3">
           <div class="flex-1 min-w-0">
@@ -384,19 +476,34 @@
               {#if isUnlisted(a.privacy)}
                 <span class="text-zinc-500 shrink-0" title="Unlisted">🔒</span>
               {/if}
-              <a
-                href={a.detail_url ? `${import.meta.env.BASE_URL}activity/${a.id}/` : `${import.meta.env.BASE_URL}activity/local/?id=${a.id}`}
-                class="before:absolute before:inset-0 before:content-[''] truncate"
-                on:click={() => { try { sessionStorage.setItem(`bincio:activity:${a.id}`, JSON.stringify(a)); } catch {} }}
-              >{a.title}</a>
+              {#if selectMode}
+                <span class="truncate">{a.title}</span>
+              {:else}
+                <a
+                  href={a.detail_url ? `${import.meta.env.BASE_URL}activity/${a.id}/` : `${import.meta.env.BASE_URL}activity/local/?id=${a.id}`}
+                  class="before:absolute before:inset-0 before:content-[''] truncate"
+                  on:click={() => { try { sessionStorage.setItem(`bincio:activity:${a.id}`, JSON.stringify(filterHandle && !a.handle ? { ...a, handle: filterHandle } : a)); } catch {} }}
+                >{a.title}</a>
+              {/if}
             </h3>
           </div>
-          <span
-            class="text-xs font-medium px-2 py-0.5 rounded-full flex-shrink-0"
-            style="background:{sportColor(a.sport)}22; color:{sportColor(a.sport)}"
-          >
-            {sportIcon(a.sport)} {sportLabel(a.sport, a.sub_sport)}
-          </span>
+          {#if selectMode}
+            <div
+              class="shrink-0 w-5 h-5 rounded-full border-2 flex items-center justify-center transition-colors"
+              class:border-zinc-600={!isSelected}
+              class:border-[--accent]={isSelected}
+              style={isSelected ? 'background:var(--accent)' : ''}
+            >
+              {#if isSelected}<span class="text-[10px] text-white leading-none">✓</span>{/if}
+            </div>
+          {:else}
+            <span
+              class="text-xs font-medium px-2 py-0.5 rounded-full flex-shrink-0"
+              style="background:{sportColor(a.sport)}22; color:{sportColor(a.sport)}"
+            >
+              {sportIcon(a.sport)} {sportLabel(a.sport, a.sub_sport)}
+            </span>
+          {/if}
         </div>
 
         <!-- track thumbnail -->
@@ -466,3 +573,35 @@
     </div>
   {/if}
 {/if}
+
+<!-- Bulk action bar — fixed at bottom when select mode is active -->
+{#if selectMode}
+  <div class="fixed bottom-0 left-0 right-0 z-50 flex items-center justify-center gap-3 px-4 py-4 bg-zinc-950/95 backdrop-blur border-t border-zinc-800">
+    <span class="text-sm text-zinc-400 mr-2">
+      {selected.size} selected
+    </span>
+    <button
+      class="px-4 py-2 rounded-lg border border-red-700 text-red-400 hover:bg-red-900/30 disabled:opacity-40 transition-colors text-sm"
+      disabled={selected.size === 0 || bulkWorking}
+      on:click={_deleteSelected}
+    >
+      Delete ({selected.size})
+    </button>
+    <button
+      class="px-4 py-2 rounded-lg border border-zinc-600 text-zinc-300 hover:bg-zinc-800 disabled:opacity-40 transition-colors text-sm"
+      disabled={selected.size < 2 || bulkWorking}
+      on:click={_mergeSelected}
+    >
+      Merge ({selected.size})
+    </button>
+    <button
+      class="px-4 py-2 rounded-lg border border-zinc-700 text-zinc-500 hover:text-zinc-300 transition-colors text-sm"
+      on:click={_exitSelect}
+    >
+      Cancel
+    </button>
+    {#if bulkWorking}
+      <span class="text-xs text-zinc-500">Working…</span>
+    {/if}
+  </div>
+{/if}

site/src/lib/types.ts

@@ -130,6 +130,8 @@ export interface ActivityDetail extends Omit<ActivitySummary, 'detail_url' | 'tr
   source_file?: string | null;
   download_disabled?: boolean;
   custom: Record<string, unknown>;
+  /** IDs of secondary activities merged into this one (set by /api/merge). */
+  merged_ids?: string[] | null;
 }
 
 export interface Lap {