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

site/src/layouts/Base.astro

@@ -7,8 +7,10 @@ interface Props {
   description?: string;
   /** Set true on pages that must remain accessible without auth (login, register). */
   public?: boolean;
+  /** Remove the content wrapper so a child can fill the remaining viewport. */
+  fullscreen?: boolean;
 }
-const { title = 'BincioActivity', description = 'Your personal activity stats', public: isPublicPage = false } = Astro.props;
+const { title = 'BincioActivity', description = 'Your personal activity stats', public: isPublicPage = false, fullscreen = false } = Astro.props;
 const editUrl      = import.meta.env.PUBLIC_EDIT_URL     ?? '';
 const wikiUrl      = import.meta.env.PUBLIC_WIKI_URL     ?? '';
 const plannerUrl   = import.meta.env.PUBLIC_PLANNER_URL  ?? '';
@@ -547,9 +549,15 @@ try {
     </div>
   )}
 
-  <main class="max-w-7xl mx-auto px-4 py-6">
-    <slot />
-  </main>
+  {fullscreen ? (
+    <main style="height:calc(100vh - 3rem);overflow:hidden">
+      <slot />
+    </main>
+  ) : (
+    <main class="max-w-7xl mx-auto px-4 py-6">
+      <slot />
+    </main>
+  )}
 
   <script>
     // Register service worker for local activity storage (offline support)