Enrich backup metadata with albums, descriptions, keywords, and people
Add four enrichment queries to Photos.sqlite reader that build lookup
maps for descriptions, albums, keywords, and identified people. Merge
into PhotoAsset during row mapping with graceful degradation when
enrichment tables are missing (schema resilience across macOS versions).
Also adds runtime validation for asset kind and cloud state values,
debug logging for unexpected query failures, and O(1) Set-based
deduplication for people data.