feat: section 5 — MapLibre map with live track and camera follow

Replace SVG TrackView with a real MapLibre map:
- OpenFreeMap liberty tiles (no API key)
- Camera follows user in course mode while recording
- GeoJSONSource + LineLayer renders track polyline updated live
- UserLocation dot shows current GPS position
- Sensors button overlaid with semi-transparent background

CLAUDE.md

@@ -121,11 +121,9 @@ Items below are what remains before v1 is shippable.
 
 - [x] `src/services/batteryOptimization.ts` — Android-only, one-time prompt (dismissed flag in AsyncStorage); uses `REQUEST_IGNORE_BATTERY_OPTIMIZATIONS` intent to open the system dialog for bincio-rec directly; falls back to `IGNORE_BATTERY_OPTIMIZATION_SETTINGS` (general page) on OEMs that block the direct intent; called from `App.tsx` on mount alongside notification permission request
 
-### 5 — Map (optional upgrade)
+### 5 — Map ✅
 
-The track view from section 1 already shows the GPX polyline scaled to fit the screen.
-MapLibre can be added later for a real basemap (streets/terrain), but is not required for v1.
-
-- [ ] **MapLibre basemap** — replace `TrackView` SVG with `<MapLibreGL.MapView>` + a tile source (e.g. OpenFreeMap); call `MapLibreGL.setAccessToken(null)` for raster-free usage
-- [ ] **Camera follow** — add `<MapLibreGL.Camera>` that follows `trackPoints[last]` during recording
-- [ ] **Line layer** — replace SVG polyline with `<MapLibreGL.ShapeSource>` + `<MapLibreGL.LineLayer>`
+- [x] **MapLibre basemap** — `Map` with OpenFreeMap liberty style (`tiles.openfreemap.org`); no API key required; logo and attribution hidden
+- [x] **Camera follow** — `Camera` with `trackUserLocation="course"` while recording; switches off when idle/paused
+- [x] **Live track line** — `GeoJSONSource` fed a memoized `LineString` from `trackPoints`; `Layer` with `type="line"` and blue stroke rendered on top of the basemap
+- [x] **User location dot** — `UserLocation` component shows current position on map