Refactor app based on senior review and add lazy album art

[scorp867]

Implement senior developer's review suggestions and add lazy album art loading with fallbacks to improve app efficiency, stability, and UI.

The changes address several areas:

• Recomposition efficiency: Switched to collectAsStateWithLifecycle for repository flows to prevent memory leaks and unnecessary recompositions.
• MediaController lifecycle: Introduced rememberMediaController and DisposableEffect for listeners to ensure proper resource management and prevent leaks.
• Data access & cleanliness: Wrapped repository lookups in Dispatchers.IO and created a resolveTrack helper to prevent UI blocking and deduplicate logic.
• UI stability: Adjusted bottom bar animation to prevent layout jumps.
• Album art: Implemented a multi-step fallback chain in SmartArtwork for robust and visually appealing lazy loading.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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