feat: v1.30.0 — Discord RPC, offline bulk download, artist images, lazy loading, crossfade fix

- Discord Rich Presence (opt-in) — requested by @Bewenben (#49)
- Bulk offline download for playlists and artist discographies — requested by @Apollosport (#54)
- Offline Library filter tabs: All / Albums / Playlists / Discographies with artist grouping
- Artist images on Artists overview (opt-in, off by default) — reported by @Apollosport (#53)
- Image lazy loading via IntersectionObserver (300px margin) across all pages
- Fix: crossfade no longer triggers on manual track skip — reported by @netherguy4 (#35)
- Fix: playlist offline cache now stored as single entry (not per-album)
- Fix: image cache AbortController no longer blocks IDB writes
- Update toast: experimental auto-update hint + GH download link always visible (Win/Mac)
- Queue tech strip: genre removed
- Facebook theme: contrast, opaque badge/back button, queue tab labels
- "Save discography offline" label (was "Download discography")
- Fix: clearing empty playlists via updatePlaylist.view (Axios empty array workaround)
- starredOverrides propagated to AlbumDetail, Favorites, RandomMix

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

src/components/AppUpdater.tsx

@@ -123,9 +123,15 @@ export default function AppUpdater() {
       {state.phase === 'available' && (
         <div className="app-updater-actions">
           {canInstall && (
-            <button className="app-updater-btn-primary" onClick={handleInstall}>
-              <Download size={12} /> {t('common.updaterInstall')}
-            </button>
+            <>
+              <p className="app-updater-hint">{t('common.updaterExperimentalHint')}</p>
+              <button className="app-updater-btn-primary" onClick={handleInstall}>
+                <Download size={12} /> {t('common.updaterInstall')}
+              </button>
+              <button className="app-updater-btn-secondary" onClick={handleDownload}>
+                <Download size={12} /> {t('common.updaterDownload')}
+              </button>
+            </>
           )}
           {isLinuxFallback && (
             <button className="app-updater-btn-primary" onClick={handleDownload}>