feat(anime): add anime browser powered by Aniyomi extensions

- Add `subminer anime` / `--anime` and a tray entry to open a browser that searches installed Aniyomi extension sources, shows cover art and episodes, and plays into mpv with overlay/mining attached
- Add an Extensions tab to add repos and install/update/remove sources, and per-source settings for sources needing config
- Support searching all sources at once with streaming, per-source results and status
- Prefer Japanese audio/subtitle tracks from the source and keep the primary subtitle slot reserved for Japanese
- Fix window/tray/Dock handling so the browser and mpv can be switched between without quitting the app or losing the Dock icon
- Add anime.repos, anime.extensionsDir, anime.preferredQuality config keys (no bundled repos or discovery)

docs-site/usage.md

@@ -70,6 +70,7 @@ subminer https://youtu.be/...     # Play a YouTube URL
 subminer stats                    # Open the immersion stats dashboard
 subminer doctor                   # Check dependencies, config, and the mpv socket
 subminer settings                 # Open the SubMiner settings window
+subminer anime                    # Open the anime browser window
 subminer app --setup              # Re-open first-run setup
 subminer -u                       # Check for updates
 ```
@@ -131,6 +132,7 @@ SubMiner.AppImage --open-tsukihime        # Open TsukiHime subtitle search
 SubMiner.AppImage --yomitan               # Open Yomitan settings
 SubMiner.AppImage --settings              # Open the SubMiner settings window
 SubMiner.AppImage --jellyfin              # Open the Jellyfin setup window
+SubMiner.AppImage --anime                 # Open the anime browser window
 SubMiner.AppImage --dictionary            # Generate a character dictionary ZIP
 SubMiner.AppImage --start --dev           # Enable app/dev mode
 SubMiner.AppImage --start --log-level debug  # Verbose logging without dev mode