1 — Timeseries split

- writer.py: timeseries is now written to {id}.timeseries.json as a separate file. The detail JSON gets a timeseries_url field instead. finalize_pending and cleanup_pending handle the extra file.
  - merge.py (merge_one): symlinks the .timeseries.json file alongside the detail JSON. merge_all already handles it transparently (the .timeseries.json stem doesn't match any activity
  ID in to_merge, so it falls through to the symlink branch).
  - types.ts: timeseries is now timeseries?: Timeseries | null, and timeseries_url?: string | null added.
  - dataloader.ts: new loadTimeseries(url, detailUrl, base) function that resolves paths correctly in both single- and multi-user modes (uses the fetched detail URL's directory as the base).
  - ActivityDetail.svelte: loads timeseries separately after detail loads; uses detail.timeseries for IDB activities (embedded) or fetches via detail.timeseries_url for server activities. Charts show a pulse placeholder while loading.

 2 — GZip

  - GZipMiddleware (min 1 KB) added to both bincio/serve/server.py and bincio/edit/server.py — all API JSON responses are now gzip-compressed.
  - For static files (the big timeseries JSONs), nginx should be configured with gzip on; gzip_types application/json application/geo+json; — no code change needed on the server side.

  Net effect: opening an activity page now fetches ~1.4 KB (detail) instead of ~586 KB. The timeseries fetches ~60–150 KB gzip-compressed shortly after (it loads concurrently with the map rendering).

bincio/extract/writer.py

@@ -50,6 +50,10 @@ def write_activity(
     source = _infer_source(activity)
     has_gps = metrics.bbox is not None and privacy not in ("no_gps", "private")
 
+    # Build timeseries once — written to a separate file to keep detail JSON small
+    timeseries = build_timeseries(activity.points, activity.started_at, privacy)
+    tag = activity.source_hash[-8:] if activity.source_hash else "unknown"
+
     # ── detail JSON ──────────────────────────────────────────────────────────
     detail: dict = {
         "bas_version": "1.0",
@@ -80,7 +84,7 @@ def write_activity(
         "best_efforts": metrics.best_efforts,
         "best_climb_m": metrics.best_climb_m,
         "laps": [_serialise_lap(lap) for lap in activity.laps],
-        "timeseries": build_timeseries(activity.points, activity.started_at, privacy),
+        "timeseries_url": f"activities/{activity_id}.timeseries.json" if timeseries else None,
         "source": source,
         "source_file": activity.source_file,
         "source_hash": activity.source_hash,
@@ -92,7 +96,6 @@ def write_activity(
 
     if pending:
         # Write to a unique pending file — no collision possible
-        tag = activity.source_hash[-8:] if activity.source_hash else "unknown"
         json_path = acts_dir / f"{activity_id}.{tag}.pending.json"
     else:
         json_path = acts_dir / f"{activity_id}.json"
@@ -104,9 +107,18 @@ def write_activity(
                 activity_id = f"{activity_id}-{activity.source_hash[-6:]}"
                 json_path = acts_dir / f"{activity_id}.json"
                 detail["id"] = activity_id
+                detail["timeseries_url"] = f"activities/{activity_id}.timeseries.json" if timeseries else None
 
     json_path.write_text(json.dumps(detail, indent=2, ensure_ascii=False))
 
+    # ── timeseries JSON (separate file — lazy-loaded by the UI) ─────────────
+    if timeseries:
+        if pending:
+            ts_path = acts_dir / f"{activity_id}.{tag}.pending.timeseries.json"
+        else:
+            ts_path = acts_dir / f"{activity_id}.timeseries.json"
+        ts_path.write_text(json.dumps(timeseries, indent=2, ensure_ascii=False))
+
     # ── GeoJSON track ────────────────────────────────────────────────────────
     if has_gps:
         geojson = build_geojson(activity.points, activity_id, epsilon=rdp_epsilon)
@@ -150,6 +162,7 @@ def finalize_pending(output_dir: Path, activity_id: str, source_hash: str) -> st
 
     pending_json = acts_dir / f"{activity_id}.{tag}.pending.json"
     pending_geojson = acts_dir / f"{activity_id}.{tag}.pending.geojson"
+    pending_ts = acts_dir / f"{activity_id}.{tag}.pending.timeseries.json"
 
     final_id = activity_id
     final_json = acts_dir / f"{final_id}.json"
@@ -165,6 +178,8 @@ def finalize_pending(output_dir: Path, activity_id: str, source_hash: str) -> st
     if final_id != activity_id and pending_json.exists():
         detail = json.loads(pending_json.read_text(encoding="utf-8"))
         detail["id"] = final_id
+        if detail.get("timeseries_url"):
+            detail["timeseries_url"] = f"activities/{final_id}.timeseries.json"
         pending_json.write_text(json.dumps(detail, indent=2, ensure_ascii=False))
 
     # Atomic rename: pending → final
@@ -180,6 +195,10 @@ def finalize_pending(output_dir: Path, activity_id: str, source_hash: str) -> st
             pending_geojson.write_text(json.dumps(geo, indent=2, ensure_ascii=False))
         pending_geojson.rename(final_geojson)
 
+    final_ts = acts_dir / f"{final_id}.timeseries.json"
+    if pending_ts.exists():
+        pending_ts.rename(final_ts)
+
     return final_id
 
 
@@ -187,7 +206,7 @@ def cleanup_pending(output_dir: Path, activity_id: str, source_hash: str) -> Non
     """Remove pending files for a losing activity (the one not chosen as canonical)."""
     acts_dir = output_dir / "activities"
     tag = source_hash[-8:] if source_hash else "unknown"
-    for suffix in (".pending.json", ".pending.geojson"):
+    for suffix in (".pending.json", ".pending.geojson", ".pending.timeseries.json"):
         p = acts_dir / f"{activity_id}.{tag}{suffix}"
         p.unlink(missing_ok=True)