GPX export: button in session detail, standard GPX 1.1 format.
Background GPS fixes:
- Native service: batched writes (10s flush) instead of per-point
appendText — eliminates race condition with reader
- JS reader: skip corrupt lines, sort by timestamp, track by ts
instead of line count — handles partial writes and reordering
- Recovery: idempotent import using max DB timestamp
- Live recording: seq numbers on every point
- FileObserver watches correct path (app root, not files/dev.baldav.app)
- Removed ACCESS_BACKGROUND_LOCATION (causes throttling)
Nav: "Трекинг" button on GPS screen when recording active.
