feat(health): optimize library sync memory and recovery logic

[drondeseries]

This PR provides critical memory optimizations and finalized path recovery:

• Memory Optimization: Replaced high-contention mutex slices with a buffered channel collector during library sync. This significantly reduces memory spikes when processing large libraries (50k+ files).
• Safe Recovery: Finalized the folder-agnostic path recovery logic that automatically heals broken library_path records.
• Absolute Path Enforcement: Ensures all recovered paths are absolute to prevent repair failures.
• Performance: Improved concurrency handling in the library sync worker.