feat(sidebar): add Playlists to favorites quick access menu

Remove filter that excluded playlists from sidebar favorites section.
Add ListMusic icon for the playlists tab in both expanded and
collapsed popover views.

Closes #233

cc

src/lib/components/Sidebar.svelte

@@ -135,7 +135,7 @@
 
   // Favorites section state
   let favoritesExpanded = $state(false);
-  let favoritesTabOrder = $state<string[]>(['tracks', 'albums', 'artists']);
+  let favoritesTabOrder = $state<string[]>(['tracks', 'albums', 'artists', 'playlists']);
   let showFavoritesMenu = $state(false);
   let favoritesMenuPos = $state({ x: 0, y: 0 });
 
@@ -933,8 +933,7 @@
   async function loadFavoritesPreferences() {
     try {
       const prefs = await invoke<FavoritesPreferences>('v2_get_favorites_preferences');
-      // Filter out 'playlists' from tab order for sidebar display
-      favoritesTabOrder = (prefs.tab_order || ['tracks', 'albums', 'artists']).filter(tab => tab !== 'playlists');
+      favoritesTabOrder = prefs.tab_order || ['tracks', 'albums', 'artists', 'playlists'];
     } catch (err) {
       console.debug('[Sidebar] Failed to load favorites preferences:', err);
     }
@@ -1514,6 +1513,8 @@
                     <Disc size={14} />
                   {:else if tab === 'tracks'}
                     <Music size={14} />
+                  {:else if tab === 'playlists'}
+                    <ListMusic size={14} />
                   {/if}
                 {/snippet}
               </NavigationItem>
@@ -1889,6 +1890,8 @@
           <Disc size={14} />
         {:else if tab === 'tracks'}
           <Music size={14} />
+        {:else if tab === 'playlists'}
+          <ListMusic size={14} />
         {/if}
         <span>{$t(`favorites.${tab}`)}</span>
       </button>