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/serve/server.py

@@ -17,6 +17,7 @@ from typing import Any, Optional
 
 from fastapi import Cookie, FastAPI, File, HTTPException, Request, Response, UploadFile
 from fastapi.middleware.cors import CORSMiddleware
+from fastapi.middleware.gzip import GZipMiddleware
 from fastapi.responses import JSONResponse
 
 from bincio.serve.db import (
@@ -61,6 +62,7 @@ def _get_data_dir() -> Path:
 
 app = FastAPI(title="BincioActivity Serve", docs_url=None, redoc_url=None)
 
+app.add_middleware(GZipMiddleware, minimum_size=1024)
 app.add_middleware(
     CORSMiddleware,
     allow_origin_regex=r"https?://localhost(:\d+)?",