feat: in-app update downloader with progress, Gitea auto-push hook

- update_checker: Gitea at git.steggi-matrix.work, Windows + Android support, asset URL detection
- update_download_dialog: animated Pyramid logo, progress bar, platform install (exe/apk)
- update_banner: Herunterladen button triggers dialog, dismiss option
- Android: REQUEST_INSTALL_PACKAGES permission + FileProvider for APK install
- post-commit hook: auto-push to Gitea on every commit
- chat_input: larger send button (60px desktop), more padding, bigger icon
- rooms_panel: space menu visible on mobile (leave space fix)
- docs: feature-checklist.md added

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pubspec.yaml

@@ -16,6 +16,7 @@ dependencies:
   matrix: ^6.2.0
   flutter_vodozemac: ^0.5.0
   flutter_secure_storage: ^10.0.0
+  sqflite: ^2.4.2
   sqflite_common_ffi: ^2.3.7+1
   sqlcipher_flutter_libs: ^0.6.8
 
@@ -33,6 +34,14 @@ dependencies:
   # UI
   dynamic_color: ^1.8.1
   google_fonts: ^6.2.1
+  flutter_svg: ^2.0.17
+  lottie: ^3.3.2
+  pretty_qr_code: ^3.6.0
+  qr: ^3.0.2
+
+  # Cryptography (for E2EE key export/import)
+  crypto: ^3.0.3
+  pointycastle: ^4.0.0
 
   # Utilities
   shared_preferences: ^2.5.5
@@ -42,11 +51,24 @@ dependencies:
   http: ^1.6.0
   mime: ^2.0.0
   collection: ^1.18.0
+  url_launcher: ^6.3.0
+  package_info_plus: ^8.1.0
+
+  # File handling
+  file_picker: ^8.1.7
+  desktop_drop: ^0.4.4
+  open_file_plus: ^3.4.1
+
+  # Media playback
+  media_kit: ^1.1.11
+  media_kit_video: ^1.2.5
+  media_kit_libs_video: ^1.0.5
 
 dev_dependencies:
   flutter_test:
     sdk: flutter
   flutter_lints: ^6.0.0
+  flutter_launcher_icons: ^0.13.1
 
 dependency_overrides:
   webcrypto: