feat(server): add websocket events for activity changes

- Add 'activity.change' event to event repository
- Emit event when new activity (reaction/comment) is created
- Add notification handler to broadcast activity changes to relevant users
- Update frontend websocket types to include on_activity_change event
- Update tests to mock album repository calls

web/src/lib/stores/websocket.ts

@@ -16,6 +16,7 @@ export interface ReleaseEvent {
 export interface Events {
   on_upload_success: (asset: AssetResponseDto) => void;
   on_user_delete: (id: string) => void;
+  on_activity_change: (data: { albumId: string; assetId: string | null }) => void;
   on_album_update: (data: { albumId: string; assetId: string[]; status: 'added' | 'removed' }) => void;
   on_asset_person: ({
     assetId,
@@ -27,7 +28,7 @@ export interface Events {
   }) => void;
   on_asset_delete: (assetId: string) => void;
   on_asset_trash: (assetIds: string[]) => void;
-  on_asset_update: (asset: AssetResponseDto) => void;
+  on_asset_update: (assetIds: string[]) => void;
   on_asset_hidden: (assetId: string) => void;
   on_asset_restore: (assetIds: string[]) => void;
   on_asset_stack_update: (assetIds: string[]) => void;