- Add SyncedFile message and subdir scoping to RescanOrigin proto
- Add label, album_type, cover_url fields to UpdateMetadataRequest/MetadataResponse
- Implement OriginScanner: walk, hash, diff, ingest with live FUSE tree and content fetcher registration
- Add enrichment DB columns: enrichment_source, enriched_at, enrichment_attempts, genres_json, label, album_type, cover_url
- Add EnrichmentUpdate struct and update_enrichment DB method
- Wire BatchUpdateMetadata to write enrichment fields alongside audio metadata
- Wire gRPC server into CLI mount command with --grpc-port flag
- Pass VirtualTree and ContentFetcher to scanner so rescanned files are immediately visible and readable via FUSE
- Add MetadataService with 5 RPCs (Get, Update, Clear, Batch, Import)
- Add 11 message types for requests/responses
- Use optional fields and map for custom_tags
- Proto codegen successful, all tests pass