feat: Rust audio engine, genre mix, queue shuffle, and UX improvements (v1.2.0)

### Audio Engine
- Replace Howler.js with native Rust/rodio backend (src-tauri/src/audio.rs)
- audio_play/pause/resume/stop/seek/set_volume Tauri commands
- Generation counter cancels stale in-flight downloads on skip
- Wall-clock position tracking; audio:ended after 2 ticks near end

### Playback Persistence
- Persist currentTrack, queue, queueIndex, currentTime to localStorage
- Cold-start resume: play + seek to saved position on app restart
- Position priority: server queue > localStorage

### Random Mix
- Genre blacklist: excludeAudiobooks toggle + custom chip-based blacklist
- Clickable genre chips in tracklist to blacklist on the fly
- Super Genre Mix: 9 genres, progressive rendering, Load 10 more
- Promise.allSettled + 45s timeout for large Metal/Rock libraries
- Two-column filter panel at top of page

### Queue & UI
- Shuffle button in queue header (Fisher-Yates, keeps current track at 0)
- LiveSearch arrow key / Enter / Escape keyboard navigation
- Multi-line tooltip support (data-tooltip-wrap attribute)
- Update link uses Tauri shell open() to launch system browser
- Sidebar min-width 180px → 200px (fixes Psysonic title clipping)
- Tooltip z-index fix: main-content z-index:1 over queue panel

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

src/styles/components.css

@@ -438,7 +438,8 @@
   transition: background var(--transition-fast);
   border-radius: 0;
 }
-.search-result-item:hover { background: var(--bg-hover); }
+.search-result-item:hover,
+.search-result-item.active { background: var(--bg-hover); }
 .search-result-icon { width: 32px; height: 32px; border-radius: var(--radius-sm); background: var(--bg-hover); display: flex; align-items: center; justify-content: center; color: var(--text-muted); flex-shrink: 0; }
 .search-result-thumb { width: 32px; height: 32px; border-radius: var(--radius-sm); object-fit: cover; flex-shrink: 0; }
 .search-result-name { font-size: 13px; font-weight: 500; color: var(--text-primary); }
@@ -1415,6 +1416,12 @@
   visibility: visible;
 }
 
+[data-tooltip-wrap]::after {
+  white-space: pre-line;
+  max-width: 220px;
+  text-align: left;
+}
+
 /* Modifiers for position */
 [data-tooltip][data-tooltip-pos="bottom"]::before {
   top: 100%;

src/styles/layout.css

@@ -235,6 +235,7 @@
   overflow: hidden;
   min-width: 0;
   background: var(--bg-app);
+  z-index: 1;
 }
 
 .content-header {