fix(scanner): handle watched moves across docker libraries

Emit transfer events when watcher reconciliation moves a book between libraries. Keep file-as-book and folder-as-book watcher paths consistent across Docker, direct runs, and delayed copy-delete moves.

Closes #386

packages/types/src/scanner.ts

@@ -37,6 +37,12 @@ export interface BookMovedEvent {
   bookIds: number[];
 }
 
+export interface BookTransferredEvent {
+  fromLibraryId: number;
+  toLibraryId: number;
+  bookIds: number[];
+}
+
 export interface ScanBooksAddedEvent {
   libraryId: number;
   books: import("./book").BookCard[];