Fix album token refresh handling and stabilize album lyrics flow

[spacegrey23]

Motivation

1. Ensure album fetching does not fail with missing or expired Spotify access tokens by validating and refreshing the token before API calls.
2. Provide a clear error response when token refresh fails to avoid ambiguous failures.
3. Support fetching lyrics for every track in an album and render per-track lyrics in the client when given an album link.

Description

1. Validate and refresh currentAccessToken in backend/api/spotify/getAlbumTracks.mjs and return a structured 500 response when the token remains missing.
2. Add backend/api/getAlbumLyrics.mjs which iterates album tracks and attempts to collect lyrics via getLyricsBySignature, getLyricsByQuery, and getLyricsFromSpotify.
3. Register GET /getAlbumData in backend/api/routes/routes.mjs and add album detection to client/src/features/lyrics/useLyrics.js and client/src/hooks/useLyrics.js to route requests to the correct endpoint.
4. Update client/src/App.jsx to detect album responses and render a list of per-track LyricsCard components, and add backend/test/spotify.test.mjs for parseAlbumId.

Testing

1. Ran unit tests with node --test backend/test/spotify.test.mjs.
2. All tests passed: 3 passed, 0 failed.
3. No end-to-end or integration tests were run; album endpoint behavior requires valid Spotify credentials for manual verification.
4. The added test verifies parseAlbumId for open.spotify.com and spotify:album: formats and an invalid URL case.

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[chatgpt-codex-connector]

Avoid spreading null in album error handler

If an exception occurs before albumData is assigned (e.g., a Spotify API/network error in getAlbumTracks), the catch falls through to the 404 response and spreads albumData || null. Spreading null/undefined throws a TypeError, so the error handler itself fails and the request ends up as an unhandled 500 instead of a clean error response. This path is reachable whenever the try block throws before albumData is set; consider guarding with albumData ? { ...albumData } : {} or similar.

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