fix: saved tracks browser, GPX import persistence

Saved tracks browser:
- TrackDetailSheet converted from BottomSheetDialogFragment to Fragment so
  it fills the overlay instead of floating over the map
- Adapter tap pushes detail fragment onto the back stack; back button returns
  to the list naturally via popBackStack()
- SavedTracksFragment back button calls hideOverlays() (made internal) to
  close the overlay and return to the map
- Layout updated to full-screen: header with back button, RecyclerView fills
  remaining space via layout_weight instead of fixed 300dp

GPX import persistence:
- TrackRepository.importTrack() saves parsed points to Documents/Nav/ via
  TrackStorage (URI is persisted to SharedPreferences) and adds to
  in-memory list
- MainViewModel.addImportedTrack() now calls importTrack() so files opened
  via the GPX handler load on future launches

https://claude.ai/code/session_01DNjbYxiC1cco83dArNGW3G

0 files changed, 0 insertions, 0 deletions