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/cli.py

@@ -22,6 +22,24 @@ from bincio.reextract_cmd import reextract_originals  # noqa: E402
 from bincio.sync_strava import sync_strava_cmd        # noqa: E402
 from bincio.segments.cli import segments_group        # noqa: E402
 
+
+@main.command("bake-tracks")
+@click.option("--data-dir", required=True, help="BAS data store directory.")
+@click.option("--handle", default=None, help="Bake one user only (default: all).")
+def bake_tracks_cmd(data_dir: str, handle: str | None) -> None:
+    """Pre-bake GPS tracks.json for the Explore heatmap page."""
+    from pathlib import Path
+    from bincio.explore import bake_tracks
+    from bincio.render.cli import _user_dirs
+    from rich.console import Console
+    console = Console()
+    data = Path(data_dir).expanduser().resolve()
+    targets = [data / handle] if handle else _user_dirs(data)
+    for user_dir in targets:
+        n = bake_tracks(user_dir.name, data)
+        console.print(f"  [cyan]{user_dir.name}[/cyan]: {n} track(s) baked")
+
+
 main.add_command(extract)
 main.add_command(render)
 main.add_command(edit)