fix: Add save_to_disk method to MockStorage

- Fixed AttributeError when API shuts down with mock storage
- MockStorage now has public async save_to_disk method
- Periodic persistence works correctly with mock backend

Author: raold

.claude/settings.local.json

@@ -150,7 +150,8 @@
       "Bash(--notes-file RELEASE_NOTES_v4.2.3.md)",
       "Bash(tree:*)",
       "Bash(kill:*)",
-      "Bash(bash:*)"
+      "Bash(bash:*)",
+      "Bash(USE_MOCK_DB=true timeout 5 .venv/bin/uvicorn app.main:app --port 8001)"
     ],
     "deny": []
   }

app/storage/mock_storage.py

@@ -43,6 +43,10 @@ def _save_to_disk(self):
         except Exception as e:
             print(f"⚠️ Could not save memories: {e}")
 
+    async def save_to_disk(self):
+        """Public async method for periodic persistence"""
+        self._save_to_disk()
+    
     async def create_memory(self, data: Dict) -> Dict:
         """Create a new memory"""
         memory_id = str(uuid.uuid4())