Adds a synchronous, key-free snapshot() returning LibrarySnapshot (one PhotoRecord per fileID, deduped, newest first) with edited-name/time precedence (pubMagicMetadata over basic metadata) in milliseconds, plus AlbumRecord (favorites identified by type). subscribe({onChange}) delivers LibraryChange (changed/removed albums and files, refreshedAt) only when a refresh changes something; unsubscribe stops delivery. Built on the existing refresh loop; served from RAM, safe to send over IPC.
Model: opus-4-8
