feat(12-01): implement library CRUD methods and orphan cleanup pipeline

- Add AddLibrary, RenameLibrary, RemoveLibrary, GetRemovalImpact methods
- RemoveLibrary follows exact order: phantom populate → delete audio_files → orphan cleanup → commit → FTS5 rebuild → cover art file cleanup → queue compact → events
- Add cancelLibraryScan and currentTrackBelongsToLibrary helpers
- Add RemovalHooks type and removalHooks field on Library struct
- Add LibraryAdded, LibraryRenamed, LibraryRemoved event constants
- Regenerate frontend events.ts with new CRUD events
- All hand-crafted SQL has SAFETY comments per project convention
- Dual artist_credit FK check (recordings + release_groups) for orphan cleanup

frontend/src/events.ts

@@ -42,6 +42,11 @@ export const Events = {
     // Scan queue events
     LibraryScanQueued: "LibraryScanQueued",
     LibraryScanQueueDrained: "LibraryScanQueueDrained",
+
+    // Library CRUD events
+    LibraryAdded: "LibraryAdded",
+    LibraryRenamed: "LibraryRenamed",
+    LibraryRemoved: "LibraryRemoved",
 } as const;
 
 export type EventName = (typeof Events)[keyof typeof Events];