add webview map, bike reservation, and desktop entry

- Replace list view with Leaflet.js WebView map with marker clustering
- Add floating action buttons over map (Rent, Show Rentals)
- Click station markers to show bikes with Rent/Reserve buttons
- Add bike type filter menu (All/Standard/E-bikes)
- Support bike reservations via booking API
- Show reserved bikes in rentals overview
- Add desktop entry for app launchers
- Update dependencies: webkit6 0.6, gtk4 0.11, libadwaita 0.9

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

org.nextbike.NextCompanion.yml

@@ -37,6 +37,8 @@ modules:
             /app/bin/next-companion
       - install -Dm644 data/icons/org.nextbike.NextCompanion.png
           /app/share/icons/hicolor/512x512/apps/org.nextbike.NextCompanion.png
+      - install -Dm644 data/org.nextbike.NextCompanion.desktop
+          /app/share/applications/org.nextbike.NextCompanion.desktop
     sources:
       - type: dir
         path: .