Ad and purchases enabled (still need actual testing)

lib/services/cloud/cloud_storage_provider.dart

@@ -95,6 +95,16 @@ abstract class CloudStorageSession {
   /// if none exists. If duplicates exist, the earliest-created one wins.
   Future<String> findOrCreateFolder({required String parentId, required String name});
 
+  /// Relocates the existing folder [folderId] to be a child of
+  /// [newParentId] instead of wherever it currently lives, preserving its
+  /// contents and (name/subtree) intact. Used when the user picks a
+  /// different location for the app's already-existing folder (see
+  /// [CloudSyncService.selectAppFolder]), so its synced data and receipts
+  /// move with it instead of being abandoned in place while a fresh, empty
+  /// folder is created at the new location. Returns the folder's
+  /// (possibly new, for a path-addressed provider) id.
+  Future<String> moveFolder({required String folderId, required String newParentId});
+
   /// Looks up a file's ID + versionTag by name within [folderId] without
   /// downloading its content, or null if no such file exists yet.
   Future<CloudFileInfo?> findFile({required String folderId, required String name});