chore: Improve desktop integration and AppImage metadata for release

- Add Comment field to all .desktop files for app launcher descriptions
- Change category from Music to AudioVideo for better categorization
- Add Keywords for improved searchability (audiophile, hifi, streaming)
- Enhance metainfo.xml with detailed feature list and links
- Configure AppImage bundle settings in tauri.conf.json
- Update workflows to generate improved .desktop files

AppImage now includes embedded icon via Tauri icon configuration.
App will now appear in Multimedia category with proper description in all Linux app launchers.

packaging/arch/qbz.desktop

@@ -1,9 +1,11 @@
 [Desktop Entry]
 Name=QBZ
+Comment=Native Qobuz client with hi-res audio support
 Exec=qbz %u
 Type=Application
 Icon=qbz
-Categories=Audio;Music;Player;
+Categories=AudioVideo;Audio;Music;Player;
 Terminal=false
 StartupWMClass=QBZ
+Keywords=music;audio;qobuz;hifi;streaming;audiophile;
 MimeType=x-scheme-handler/qbz;