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

src-tauri/tauri.conf.json

@@ -1,6 +1,6 @@
 {
-  "productName": "Bocken Fitness",
-  "identifier": "org.bocken.fitness",
+  "productName": "Bocken",
+  "identifier": "org.bocken.app",
   "version": "0.1.0",
   "build": {
     "devUrl": "http://192.168.1.4:5173",
@@ -10,8 +10,8 @@
     "withGlobalTauri": true,
     "windows": [
       {
-        "title": "Bocken Fitness",
-        "url": "/fitness",
+        "title": "Bocken",
+        "url": "/",
         "fullscreen": false,
         "useHttpsScheme": true
       }