Explore: personal GPS heatmap tab under Athlete page

- bincio/explore.py: bake_tracks() simplifies GPS coords (RDP ε=0.0001),
  strips to [lng,lat], groups by sport type, writes per-handle tracks.json
- bake-tracks CLI command; render CLI calls _bake_tracks() after each build;
  strava_zip runs it once at end of batch
- /api/me/tracks endpoint serves the baked file; wipe_user cleans it up
- Explore.svelte: MapLibre full-screen map with sidebar — type pills,
  year/month date filter, Lines / Heatmap (global or by-type) view modes
- AthleteView: Explore tab visible only to profile owner (checks __bincioMe)
- Base.astro: fullscreen prop + Planner nav link

bincio/serve/routers/uploads.py

@@ -487,6 +487,11 @@ async def upload_strava_zip(
                              user.handle, imported_count, error_count)
                     if any_imported:
                         merge_all(dd)
+                        try:
+                            from bincio.explore import bake_tracks
+                            bake_tracks(user.handle, deps._get_data_dir())
+                        except Exception as exc:
+                            log.warning("strava-zip[%s]: bake_tracks failed (non-fatal): %s", user.handle, exc)
                         tasks._trigger_rebuild(user.handle)
         except Exception as exc:
             log.error("strava-zip[%s]: fatal error: %s", user.handle, exc, exc_info=True)