v0.9.5: The Voltron Update — modular architecture, stable IDs, parallelized boot

- Parallelized startup (60s → 15s) via ThreadPoolExecutor
- Adaptive polling engine with ETag caching (no more bbox interrupts)
- useCallback optimization for interpolation functions
- Sliding LAYERS/INTEL edge panels replace bulky Record Panel
- Modular fetcher architecture (flights, geo, infrastructure, financial, earth_observation)
- Stable entity IDs for GDELT & News popups (PR #63, credit @csysp)
- Admin auth (X-Admin-Key), rate limiting (slowapi), auto-updater
- Docker Swarm secrets support, env_check.py validation
- 85+ vitest tests, CI pipeline, geoJSON builder extraction
- Server-side viewport bbox filtering reduces payloads 80%+

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Former-commit-id: f2883150b5bc78ebc139d89cc966a76f7d7c0408

backend/.env.example

@@ -18,3 +18,6 @@ AIS_API_KEY=              # https://aisstream.io/ — free tier WebSocket key
 # If unset, these endpoints remain open (fine for local dev).
 # Set this in production and enter the same key in Settings → Admin Key.
 # ADMIN_KEY=your-secret-admin-key-here
+
+# LTA Singapore traffic cameras — leave blank to skip this data source.
+# LTA_ACCOUNT_KEY=