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/components/AppUpdater.tsx

@@ -200,13 +200,10 @@ export default function AppUpdater() {
   };
 
   const handleShowFolder = async () => {
-    try {
-      const dir = await dirname(dlPath);
-      await open(dir);
-    } catch {
-      // fallback: try opening the file path directly
-      await open(dlPath).catch(() => {});
-    }
+    // tauri-plugin-shell's open() only allows https:// per capability scope —
+    // local paths are blocked and fail silently. Delegate to Rust instead.
+    const dir = await dirname(dlPath);
+    await invoke('open_folder', { path: dir });
   };
 
   const pct = dlProgress.total > 0