perf(shuffle): Implement paginated shuffle with seeded deterministic …

[Alexzafra13]

…ordering

• Replace findAllShuffled with findShuffledPaginated in ITrackRepository
• Use md5(id || seed) for deterministic ordering in PostgreSQL
• Add seed, skip, take params to GET /tracks/shuffle endpoint
• Return hasMore, seed, skip, take in response for pagination
• Update frontend tracksService with new ShuffledTracksResponse type
• Refactor useShufflePlay hook for batch loading with auto-prefetch
• Create unit tests for GetShuffledTracksUseCase
• Update existing tests with new repository method

Benefits:

• Reduces initial payload from ~3600 tracks to 50 tracks
• Enables infinite scrolling through shuffle queue
• Same seed produces same order for consistent pagination