feat: Spotify integration (OAuth + voice tools)

lib/spotify-client.ts

@@ -0,0 +1,34 @@
+let cachedToken: { token: string; expiresAt: number } | null = null
+
+export async function getAccessToken(): Promise<string> {
+  if (cachedToken && Date.now() < cachedToken.expiresAt - 30_000) {
+    return cachedToken.token
+  }
+
+  const refreshToken = process.env.SPOTIFY_REFRESH_TOKEN
+  if (!refreshToken) throw new Error('SPOTIFY_REFRESH_TOKEN not set')
+
+  const clientId = process.env.SPOTIFY_CLIENT_ID!
+  const clientSecret = process.env.SPOTIFY_CLIENT_SECRET!
+
+  const res = await fetch('https://accounts.spotify.com/api/token', {
+    method: 'POST',
+    headers: {
+      'Content-Type': 'application/x-www-form-urlencoded',
+      Authorization: `Basic ${Buffer.from(`${clientId}:${clientSecret}`).toString('base64')}`,
+    },
+    body: new URLSearchParams({
+      grant_type: 'refresh_token',
+      refresh_token: refreshToken,
+    }),
+  })
+
+  const data = await res.json()
+  if (!data.access_token) throw new Error(`Spotify token refresh failed: ${JSON.stringify(data)}`)
+
+  cachedToken = {
+    token: data.access_token,
+    expiresAt: Date.now() + (data.expires_in || 3600) * 1000,
+  }
+  return cachedToken.token
+}