chore: upgrade tooling stack

- TypeScript 3.9 -> 5.8
- ESLint 6 -> 9 (flat config)
- Prettier 1 -> 3
- eslint-plugin-vue 6 -> 9
- Add vue-tsc for type checking
- Migrate Sass @import to @use syntax
- Fix Pinia persistence config for v4
- Add Spotify type declarations
- Remove unused registerServiceWorker.ts

src/types/spotify.d.ts

@@ -0,0 +1,42 @@
+declare global {
+  interface SpotifyPlayer {
+    connect(): Promise<boolean>
+    disconnect(): void
+    addListener(event: string, callback: (data: unknown) => void): void
+    removeListener(event: string, callback?: (data: unknown) => void): void
+    getCurrentState(): Promise<SpotifyPlayerState | null>
+    resume(): Promise<void>
+    pause(): Promise<void>
+    togglePlay(): Promise<void>
+    seek(position_ms: number): Promise<void>
+    previousTrack(): Promise<void>
+    nextTrack(): Promise<void>
+  }
+
+  interface SpotifyPlayerState {
+    paused: boolean
+    track_window?: {
+      current_track?: {
+        name: string
+      }
+    }
+  }
+
+  interface SpotifyPlayerConstructorOptions {
+    name: string
+    getOAuthToken: (callback: (token: string) => void) => void
+  }
+
+  interface SpotifyNamespace {
+    Player: new (options: SpotifyPlayerConstructorOptions) => SpotifyPlayer
+  }
+
+  interface Window {
+    onSpotifyWebPlaybackSDKReady?: () => void
+    Spotify: SpotifyNamespace
+  }
+
+  const Spotify: SpotifyNamespace
+}
+
+export {}