feat(random-mix): context-aware remix button + genre reset chip

Remix button now targets the active context: relabels to "{{genre}} neu
mixen" when a genre is selected and re-fetches that genre instead of the
global random pool. "Alle Songs" chip added as first genre option to
reset back to the full library mix without leaving the page.

Also fixes album-grid cards stretching to full page height on macOS
WebKit (align-items: start on .album-grid-wrap).

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

src/pages/RandomMix.tsx

@@ -182,8 +182,17 @@ export default function RandomMix() {
         <h1 className="page-title">{t('randomMix.title')}</h1>
 
         <div style={{ display: 'flex', gap: '0.5rem' }}>
-          <button className="btn btn-surface" onClick={fetchSongs} disabled={loading} data-tooltip={t('randomMix.remixTooltip')}>
-            <RefreshCw size={18} className={loading ? 'spin' : ''} /> {t('randomMix.remix')}
+          <button
+            className="btn btn-surface"
+            onClick={selectedGenre ? () => loadGenreMix(selectedGenre) : fetchSongs}
+            disabled={selectedGenre ? genreMixLoading : loading}
+            data-tooltip={selectedGenre
+              ? t('randomMix.remixTooltipGenre', { genre: selectedGenre })
+              : t('randomMix.remixTooltip')
+            }
+          >
+            <RefreshCw size={18} className={(selectedGenre ? genreMixLoading : loading) ? 'spin' : ''} />
+            {selectedGenre ? t('randomMix.remixGenre', { genre: selectedGenre }) : t('randomMix.remix')}
           </button>
           {(() => {
             const isGenreLoading = selectedGenre && !genreMixComplete;
@@ -313,6 +322,14 @@ export default function RandomMix() {
               <span style={{ fontSize: 12, color: 'var(--text-muted)' }}>{t('randomMix.genreMixNoGenres')}</span>
             ) : (
               <>
+                <button
+                  className={`btn ${selectedGenre === null ? 'btn-primary' : 'btn-surface'}`}
+                  style={{ fontSize: 12, padding: '4px 12px' }}
+                  onClick={() => { setSelectedGenre(null); setGenreMixSongs([]); setGenreMixComplete(false); fetchSongs(); }}
+                  disabled={genreMixLoading}
+                >
+                  {t('randomMix.genreMixAll')}
+                </button>
                 {displayedGenres.map(genre => (
                   <button
                     key={genre}