Update app.py

app.py

@@ -363,6 +363,18 @@ def _atomic_write_json(path, data):
         json.dump(data, f, ensure_ascii=False, indent=2)
     os.replace(tmp, path)
 
+def _load_json(path, default):
+    if os.path.exists(path):
+        try:
+            with open(path, "r", encoding="utf-8") as f:
+                return json.load(f)
+        except (json.JSONDecodeError, IOError):
+            return default
+    return default
+
+def _save_json(path, data):
+    _atomic_write_json(path, data)
+
 class KnowledgeStore:
     def __init__(self, storage_path: str):
         self.base = _Path(storage_path)