refactor: extract shared types to $lib/types/

Move type definitions to centralized location:
- Qobuz API types (QobuzTrack, QobuzAlbum, QobuzArtist)
- UI display types (Track, AlbumDetail, ArtistDetail, PlaylistTrack)
- Local library types (LocalLibraryTrack)
- External API types (SongLinkResponse)

Reduces +page.svelte from 1806 to 1675 lines.

src/lib/types/index.ts

@@ -0,0 +1,162 @@
+/**
+ * Shared Type Definitions
+ *
+ * Central location for types used across the application.
+ */
+
+// ============ Qobuz API Types ============
+// Raw response types from Qobuz API (via backend)
+
+export interface QobuzImage {
+  small?: string;
+  thumbnail?: string;
+  large?: string;
+}
+
+export interface QobuzTrack {
+  id: number;
+  title: string;
+  duration: number;
+  album?: {
+    id?: string;
+    title: string;
+    image?: QobuzImage;
+  };
+  performer?: { id?: number; name: string };
+  hires_streamable?: boolean;
+  maximum_bit_depth?: number;
+  maximum_sampling_rate?: number;
+  isrc?: string;
+}
+
+export interface QobuzAlbum {
+  id: string;
+  title: string;
+  artist: { id?: number; name: string };
+  image: QobuzImage;
+  release_date_original?: string;
+  hires_streamable?: boolean;
+  tracks_count?: number;
+  duration?: number;
+  label?: { name: string };
+  genre?: { name: string };
+  maximum_bit_depth?: number;
+  maximum_sampling_rate?: number;
+  tracks?: { items: QobuzTrack[] };
+}
+
+export interface QobuzArtist {
+  id: number;
+  name: string;
+  image?: QobuzImage;
+  albums_count?: number;
+  biography?: {
+    summary?: string;
+    content?: string;
+    source?: string;
+  };
+  albums?: {
+    items: QobuzAlbum[];
+    total: number;
+    offset: number;
+    limit: number;
+  };
+}
+
+// ============ UI Display Types ============
+// Converted/formatted types for UI components
+
+export interface Track {
+  id: number;
+  number: number;
+  title: string;
+  artist?: string;
+  duration: string;
+  durationSeconds: number;
+  quality?: string;
+  hires?: boolean;
+  bitDepth?: number;
+  samplingRate?: number;
+  albumId?: string;
+  artistId?: number;
+  isrc?: string;
+}
+
+export interface AlbumDetail {
+  id: string;
+  artwork: string;
+  title: string;
+  artist: string;
+  artistId?: number;
+  year: string;
+  label: string;
+  genre: string;
+  quality: string;
+  trackCount: number;
+  duration: string;
+  tracks: Track[];
+}
+
+export interface ArtistDetail {
+  id: number;
+  name: string;
+  image?: string;
+  albumsCount?: number;
+  biography?: {
+    summary?: string;
+    content?: string;
+    source?: string;
+  };
+  albums: {
+    id: string;
+    title: string;
+    artwork: string;
+    year?: string;
+    quality: string;
+  }[];
+  totalAlbums: number;
+}
+
+export interface PlaylistTrack {
+  id: number;
+  number: number;
+  title: string;
+  artist?: string;
+  album?: string;
+  albumArt?: string;
+  duration: string;
+  durationSeconds: number;
+  hires?: boolean;
+  bitDepth?: number;
+  samplingRate?: number;
+  albumId?: string;
+  artistId?: number;
+  isrc?: string;
+}
+
+// ============ Local Library Types ============
+
+export interface LocalLibraryTrack {
+  id: number;
+  file_path: string;
+  title: string;
+  artist: string;
+  album: string;
+  duration_secs: number;
+  format: string;
+  bit_depth?: number;
+  sample_rate: number;
+  artwork_path?: string;
+}
+
+// ============ External API Types ============
+
+export interface SongLinkResponse {
+  pageUrl: string;
+  title?: string;
+  artist?: string;
+  thumbnailUrl?: string;
+  platforms: Record<string, string>;
+  identifier: string;
+  contentType: string;
+}

src/routes/+page.svelte

@@ -109,6 +109,19 @@
     type RepeatMode
   } from '$lib/stores/queueStore';
 
+  // Types
+  import type {
+    QobuzTrack,
+    QobuzAlbum,
+    QobuzArtist,
+    Track,
+    AlbumDetail,
+    ArtistDetail,
+    PlaylistTrack,
+    LocalLibraryTrack,
+    SongLinkResponse
+  } from '$lib/types';
+
   // Components
   import Sidebar from '$lib/components/Sidebar.svelte';
   import NowPlayingBar from '$lib/components/NowPlayingBar.svelte';
@@ -132,118 +145,6 @@
   import PlaylistModal from '$lib/components/PlaylistModal.svelte';
   import CastPicker from '$lib/components/CastPicker.svelte';
 
-  // Types
-  interface QobuzTrack {
-    id: number;
-    title: string;
-    duration: number;
-    album?: {
-      id?: string;
-      title: string;
-      image?: { small?: string; thumbnail?: string; large?: string };
-    };
-    performer?: { id?: number; name: string };
-    hires_streamable?: boolean;
-    maximum_bit_depth?: number;
-    maximum_sampling_rate?: number;
-    isrc?: string;
-  }
-
-  interface QobuzAlbum {
-    id: string;
-    title: string;
-    artist: { id?: number; name: string };
-    image: { small?: string; thumbnail?: string; large?: string };
-    release_date_original?: string;
-    hires_streamable?: boolean;
-    tracks_count?: number;
-    duration?: number;
-    label?: { name: string };
-    genre?: { name: string };
-    maximum_bit_depth?: number;
-    maximum_sampling_rate?: number;
-    tracks?: { items: QobuzTrack[] };
-  }
-
-  interface QobuzArtist {
-    id: number;
-    name: string;
-    image?: { small?: string; thumbnail?: string; large?: string };
-    albums_count?: number;
-    biography?: {
-      summary?: string;
-      content?: string;
-      source?: string;
-    };
-    albums?: {
-      items: QobuzAlbum[];
-      total: number;
-      offset: number;
-      limit: number;
-    };
-  }
-
-  interface ArtistDetail {
-    id: number;
-    name: string;
-    image?: string;
-    albumsCount?: number;
-    biography?: {
-      summary?: string;
-      content?: string;
-      source?: string;
-    };
-    albums: {
-      id: string;
-      title: string;
-      artwork: string;
-      year?: string;
-      quality: string;
-    }[];
-    totalAlbums: number;
-  }
-
-  interface Track {
-    id: number;
-    number: number;
-    title: string;
-    artist?: string;
-    duration: string;
-    durationSeconds: number;
-    quality?: string;
-    hires?: boolean;
-    bitDepth?: number;
-    samplingRate?: number;
-    albumId?: string;
-    artistId?: number;
-    isrc?: string;
-  }
-
-  interface AlbumDetail {
-    id: string;
-    artwork: string;
-    title: string;
-    artist: string;
-    artistId?: number;
-    year: string;
-    label: string;
-    genre: string;
-    quality: string;
-    trackCount: number;
-    duration: string;
-    tracks: Track[];
-  }
-
-  interface SongLinkResponse {
-    pageUrl: string;
-    title?: string;
-    artist?: string;
-    thumbnailUrl?: string;
-    platforms: Record<string, string>;
-    identifier: string;
-    contentType: string;
-  }
-
   // Auth State (from authStore subscription)
   let isLoggedIn = $state(false);
   let userInfo = $state<UserInfo | null>(null);
@@ -1050,24 +951,6 @@
     queueTrackLater(buildQueueTrackFromLocalTrack(track), true);
   }
 
-  // Handle playing a track from playlist view
-  interface PlaylistTrack {
-    id: number;
-    number: number;
-    title: string;
-    artist?: string;
-    album?: string;
-    albumArt?: string;
-    duration: string;
-    durationSeconds: number;
-    hires?: boolean;
-    bitDepth?: number;
-    samplingRate?: number;
-    albumId?: string;
-    artistId?: number;
-    isrc?: string;
-  }
-
   async function handlePlaylistTrackPlay(track: PlaylistTrack) {
     console.log('Playing playlist track:', track);
 
@@ -1126,20 +1009,6 @@
     }
   }
 
-  // Handle playing a track from local library view
-  interface LocalLibraryTrack {
-    id: number;
-    file_path: string;
-    title: string;
-    artist: string;
-    album: string;
-    duration_secs: number;
-    format: string;
-    bit_depth?: number;
-    sample_rate: number;
-    artwork_path?: string;
-  }
-
   async function handleLocalTrackPlay(track: LocalLibraryTrack) {
     console.log('Playing local track:', track);