feat: v1.8.0 — new themes, queue toolbar, lightbox, i18n (fr/nl)

Themes:
- Add Poison (phosphor green on charcoal), Nucleo (warm brass light), Classic Winamp (LCD glow, Winamp yellow/orange) themes
- Overhaul Psychowave — refined deep violet, no longer WIP
- Reorganise ThemePicker into groups: Catppuccin, Nord, Retro, Tokyo Night, Psysonic Themes
- Add --volume-accent CSS var for per-theme volume slider colour override

Queue:
- Full toolbar redesign with centred round buttons (Shuffle/Save/Load/Clear/Gapless/Crossfade)
- Crossfade popover with 1–10 s range slider, right-aligned to avoid viewport overflow
- Queue header: title + count + duration inline in accent colour, close button removed
- Tech info (codec/bitrate) as frosted-glass overlay badge on cover art

UI:
- CoverLightbox shared component for album cover (AlbumHeader) and artist avatar (ArtistDetail)
- NowPlayingDropdown: separate spinning/loading state — button always clickable, icon spins 600 ms min
- Settings: "Experimental" badge on Crossfade and Gapless toggles
- Help page: 2-column grid layout, new Crossfade & Gapless Q&A entry, updated theme/language entries

i18n:
- Full French (fr) and Dutch (nl) translations across all namespaces
- Language selector sorted alphabetically (nl, en, fr, de)

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

src/components/NowPlayingDropdown.tsx

@@ -14,6 +14,7 @@ export default function NowPlayingDropdown() {
   const isPlaying = usePlayerStore(s => s.isPlaying);
   const ownUsername = useAuthStore(s => s.getActiveServer()?.username ?? '');
   const [loading, setLoading] = useState(false);
+  const [spinning, setSpinning] = useState(false);
   const dropdownRef = useRef<HTMLDivElement>(null);
 
   const fetchNowPlaying = async () => {
@@ -28,6 +29,13 @@ export default function NowPlayingDropdown() {
     }
   };
 
+  const handleRefresh = () => {
+    setSpinning(true);
+    fetchNowPlaying().finally(() => {
+      setTimeout(() => setSpinning(false), 600);
+    });
+  };
+
   // Poll in background so the badge stays current without opening the dropdown
   useEffect(() => {
     fetchNowPlaying();
@@ -104,11 +112,11 @@ export default function NowPlayingDropdown() {
           <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', borderBottom: '1px solid var(--border-subtle)', paddingBottom: '0.5rem' }}>
             <h3 style={{ margin: 0, fontSize: '14px', fontWeight: 600 }}>{t('nowPlaying.title')}</h3>
             <button
-              onClick={fetchNowPlaying}
-              className={`btn btn-ghost ${loading ? 'animate-spin' : ''}`}
-              style={{ width: '28px', height: '28px', padding: 0 }}
+              onClick={handleRefresh}
+              className="btn btn-ghost"
+              style={{ width: '28px', height: '28px', padding: 0, justifyContent: 'center' }}
             >
-              <RefreshCw size={14} />
+              <RefreshCw size={14} className={spinning ? 'animate-spin' : ''} />
             </button>
           </div>