fix: font switching, layout scaling, embedded lyrics, folder opening

- fix(fonts): update CSS var declarations to @fontsource-variable naming
  ('Inter Variable', 'Outfit Variable', etc.) so dynamic font switching works
- fix(layout): 100vh → 100% on .app-shell to fix Windows WebView2 playerbar drift;
  1fr → minmax(0,1fr) in all grid-template-rows + remove min-height: 720px to fix
  Linux playerbar disappearing at high zoom or small window sizes
- fix(updater): replace shell open() with Rust open_folder command to bypass
  shell:allow-open capability scope blocking local paths on Windows
- fix(lyrics): add get_embedded_lyrics Tauri command (id3 crate for MP3 SYLT/USLT,
  lofty for FLAC SYNCEDLYRICS/LYRICS); fix parseLrc regex for LRC without fractional
  seconds; fix SubsonicStructuredLyrics to accept both synced and issynced fields

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

src-tauri/Cargo.toml

@@ -44,6 +44,8 @@ souvlaki = { version = "0.8", default-features = false, features = ["use_zbus"]
 discord-rich-presence = "0.2"
 url = "2"
 thread-priority = "1"
+lofty = "0.22"
+id3 = "1.16.4"
 
 [patch.crates-io]
 # Local patch for Symphonia's isomp4 demuxer: