feat(ai): generate covers without new titles

app/db.py

@@ -973,6 +973,29 @@ def set_generated(task_id, new_title, new_cover_path, path=None, conn=None) -> N
                 (new_title, new_cover_path, now, now, int(task_id)),
             )
 
+
+def set_generated_cover(task_id, new_cover_path, path=None, conn=None) -> None:
+    """Persist an AI-generated cover without changing the generated title."""
+
+    now = _now()
+    with _connection(conn, path) as database:
+        with database:
+            database.execute(
+                """
+                UPDATE tasks
+                SET new_cover_path = ?,
+                    stage = 'generated',
+                    status = 'success',
+                    last_error = NULL,
+                    generate_attempts = generate_attempts + 1,
+                    generated_at = ?,
+                    updated_at = ?
+                WHERE id = ?
+                """,
+                (new_cover_path, now, now, int(task_id)),
+            )
+
+
 def update_generated_title(task_id, new_title, path=None, conn=None) -> None:
     """Update a generated title manually without touching Shopee or local cover files."""