feat(api): GET /api/spotify/track – fetch currently or recently played

[Rend1027]

• Create backend route:
  router.get("/spotify/track", authenticateJWT, async (req, res) => { ... });

Inside the controller:

• Extract user’s Spotify access token (from req.user or req.session)

• Try calling:
  GET https://api.spotify.com/v1/me/player/currently-playing

• If 204 or empty, fallback to:
  GET https://api.spotify.com/v1/me/player/recently-played?limit=1

• Extract metadata from either source:

• spotifyTrackId

• title

• artist (joined string)

• albumArt (track.album.images[0].url)

• preview_url

• Return cleaned data to frontend:

{
"spotifyTrackId": "...",
"title": "...",
"artist": "...",
"albumArt": "...",
"preview_url": "..."
}