fix(agent): add memory config validation and fix config id reference

- Add null check for actual_config_id before calling term_memory_save in langchain_agent.py to prevent errors when memory config is unavailable
- Add warning log when skipping term_memory_save due to missing memory config
- Fix incorrect attribute reference from memory_config.id to memory_config.config_id in memory_agent_service.py
- Fix method call from private _get_workspace_default_config to public get_workspace_default_config in memory_config_service.py
- Ensures graceful handling of missing memory configurations and prevents runtime errors

api/app/services/memory_config_service.py

@@ -525,7 +525,7 @@ class MemoryConfigService:
                 "No memory config ID provided, using workspace default",
                 extra={"workspace_id": str(workspace_id)}
             )
-            return self._get_workspace_default_config(workspace_id)
+            return self.get_workspace_default_config(workspace_id)
         
         config = self.db.get(MemoryConfigModel, memory_config_id)
         
@@ -540,7 +540,7 @@ class MemoryConfigService:
             }
         )
         
-        return self._get_workspace_default_config(workspace_id)
+        return self.get_workspace_default_config(workspace_id)
 
     def delete_config(
         self,