fix(migration): preserve and recover legacy desktop sources (#1550)

* fix(migration): recover legacy desktop sources without replacing current data

* test(migration): cover legacy recovery IPC contracts

* test(migration): use static legacy Electron bootstrap

libs/shared/interfaces/src/lib/electron-api.interface.ts

@@ -889,6 +889,10 @@ export interface ElectronBridgeApi {
          */
         operationId?: string
     ) => Promise<ElectronBridgeResult>;
+    dbMigrateAppPlaylists: (
+        playlists: Playlist[]
+    ) => Promise<{ success: boolean; count: number }>;
+    dbRecoverLegacyPlaylists: () => Promise<void>;
     dbUpsertAppPlaylists: (
         playlists: Playlist[]
     ) => Promise<ElectronBridgeCountResult>;