fix: startup speed, image retry, shuffle random start, genres, search badge, playlist refresh

- Remove await on fetchRomajiIndex() at startup so navigation is not blocked
  by the romaji index network call (was the main cause of 30s Android startup)
- Add window._imgRetry() with 3 retries (1.5s/3s/4.5s backoff) for all card/
  song/cover images that fail to load; falls back to emoji only after exhausting retries
- playQueue with HAS_BRIDGE + shuffle: pick a random startIdx so album/playlist
  playback starts at a random track, not always index 0
- Reduce mobile genre grid limit from 12 to 6
- Fix "Global Suche" badge text: was "iTunes Store + Local", now "iTunes Store"
- deleteSong: always refresh loadPlaylists() unconditionally (not just when
  page is active) with a 3s delay so song counts are current when navigating back

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

index.html

@@ -315,7 +315,7 @@
       <div class="page" id="page-discover">
         <div class="page-header">
           <div class="page-title"><span class="blue">Global</span> Suche</div>
-          <span class="badge badge-itunes" style="font-size:11px;padding:4px 10px">iTunes Store + Local</span>
+          <span class="badge badge-itunes" style="font-size:11px;padding:4px 10px">iTunes Store</span>
         </div>
         <div class="search-wrap" style="padding:0 0 20px">
           <div class="search-box" style="background:var(--surface);border-color:var(--border2)">