Add Optimization Analysis & Plan

[google-labs-jules]

Created a new file OPTIM.md detailing a step-by-step plan to optimize the application's performance. The analysis covers:

• UI Rendering: Identifying SubcomposeAsyncImage usage and unstable List properties in data classes as major sources of jank.
• Memory & Data Loading: Pinpointing eager loading of the entire library in PlayerViewModel and proposing a Lazy Loading strategy.
• Background Processing: flagging the manual file walking in SyncWorker as an IO bottleneck.
• Concrete actionable steps and estimated performance gains for each area.

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PR created automatically by Jules for task 14976876047548618593 started by @theovilardo

[google-labs-jules]

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