fix: load past tracks on startup; add debug logging throughout

Root cause: getPastTracks() was only called inside stopTrack(), so
saved tracks were never loaded unless a new track was recorded in
the same session. Added init{} block to MainViewModel to load them
at startup.

Logging added:
- getPastTracks(): first-call vs cached, count + point sizes
- loadViaMediaStore(): cursor row count, per-file parse attempt,
  point count per file, any openInputStream null or parse errors

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

0 files changed, 0 insertions, 0 deletions