Add comprehensive implementation plan for Calibre metadata.opf sidecar file support in the media scanner.
Key features:
- Sidecar-first approach: Calibre metadata.opf takes precedence over embedded metadata
- Complete database schema mapping (no schema changes required - all fields exist)
- Dublin Core and Calibre-specific field support
- Simplified implementation: modify existing extractMetadata() instead of wrapper pattern
- Works for all library types and file types
- Comprehensive testing strategy
Implementation details:
- ~150 lines of new code (2 new functions + 1 modification)
- No call site changes required
- Graceful degradation on malformed XML
- Performance target: <5% scan time increase
This plan reflects simplified approach based on user feedback to directly modify extractMetadata() rather than creating wrapper functions.
Related: User guide and developer docs added in separate commits