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-tauri/src/lib.rs

@@ -1,6 +1,8 @@
 // Prevents additional console window on Windows in release, DO NOT REMOVE!!
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
 
+mod audio;
+
 use tauri::{
     menu::{MenuBuilder, MenuItemBuilder},
     tray::{MouseButton, MouseButtonState, TrayIconBuilder, TrayIconEvent},
@@ -18,7 +20,10 @@ fn exit_app(app_handle: tauri::AppHandle) {
 }
 
 pub fn run() {
+    let (audio_engine, _audio_thread) = audio::create_engine();
+
     tauri::Builder::default()
+        .manage(audio_engine)
         .plugin(tauri_plugin_shell::init())
         .plugin(tauri_plugin_notification::init())
         .plugin(tauri_plugin_global_shortcut::Builder::new().build())
@@ -107,7 +112,16 @@ pub fn run() {
                 let _ = window.emit("window:close-requested", ());
             }
         })
-        .invoke_handler(tauri::generate_handler![greet, exit_app])
+        .invoke_handler(tauri::generate_handler![
+            greet,
+            exit_app,
+            audio::audio_play,
+            audio::audio_pause,
+            audio::audio_resume,
+            audio::audio_stop,
+            audio::audio_seek,
+            audio::audio_set_volume,
+        ])
         .run(tauri::generate_context!())
         .expect("error while running Psysonic");
 }