rebrand app from Bocken Fitness to Bocken, track Android project

- Manifest: name/short_name → "Bocken", start_url → "/"
- Tauri: productName → "Bocken", identifier → org.bocken.app, url → "/"
- Cargo: package → bocken, lib → bocken_lib
- Page titles: "- Fitness" → "- Bocken" across all fitness routes
- Build script: auto-regenerate android project on identifier change
- Regenerate app icon from website favicon
- Track Android project source in git (ignore only build output/caches)
- Add native GPS foreground service and AndroidBridge for background
  location tracking (LocationForegroundService, AndroidBridge.kt)
- Add ACCESS_BACKGROUND_LOCATION permission for screen-off GPS

static/manifest.json

@@ -1,8 +1,8 @@
 {
-  "name": "Bocken Rezepte",
-  "short_name": "Rezepte",
-  "description": "Eine stetig wachsende Ansammlung an Rezepten aus der Bockenschen Küche",
-  "start_url": "/rezepte",
+  "name": "Bocken",
+  "short_name": "Bocken",
+  "description": "bocken.org",
+  "start_url": "/",
   "scope": "/",
   "display": "standalone",
   "theme_color": "#5E81AC",