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/api/subsonic.ts

@@ -856,7 +856,10 @@ export interface SubsonicLyricLine {
 }
 
 export interface SubsonicStructuredLyrics {
-  issynced: boolean;
+  /** OpenSubsonic spec field name (Navidrome ≥ 0.50.0 / any OpenSubsonic server). */
+  synced?: boolean;
+  /** Legacy / alternate casing used by some older Subsonic-compatible servers. */
+  issynced?: boolean;
   lang?: string;
   offset?: number;
   displayArtist?: string;
@@ -878,7 +881,7 @@ export async function getLyricsBySongId(id: string): Promise<SubsonicStructuredL
     );
     const list = data.lyricsList?.structuredLyrics;
     if (!list || list.length === 0) return null;
-    return list.find(l => l.issynced) ?? list[0];
+    return list.find(l => l.synced || l.issynced) ?? list[0];
   } catch {
     // Server doesn't support the endpoint or track has no embedded lyrics
     return null;