feat: photo rename and viewer delete with confirmation

Backend:
- add PATCH /api/photos/:id to rename original_filename (uploader/owner/admin)
- emit photo.updated SSE event

Frontend:
- inline filename editor in the right panel
- viewer: back button (arrow_back) on the left, delete on the right
- delete confirmed via a modal dialog; filmstrip updates after deletion

frontend/src/routes/(app)/albums/[id]/+page.svelte

@@ -90,6 +90,11 @@
 				photos = photos.filter((p) => p.id !== data.id);
 				break;
 			}
+			case 'photo.updated': {
+				const photo = data as unknown as Photo;
+				photos = photos.map((p) => (p.id === photo.id ? photo : p));
+				break;
+			}
 			case 'like.added': {
 				photos = photos.map((p) =>
 					p.id === data.photo_id