feat(storage): implement unified persistence layer with database models and repositories

backend/langgraph.json

@@ -1,17 +1,12 @@
 {
   "$schema": "https://langgra.ph/schema.json",
   "python_version": "3.12",
-  "dependencies": [
-    "."
-  ],
+  "dependencies": ["."],
   "env": ".env",
   "graphs": {
     "lead_agent": "deerflow.agents:make_lead_agent"
   },
-  "auth": {
-    "path": "./app/gateway/langgraph_auth.py:auth"
-  },
   "checkpointer": {
-    "path": "./packages/harness/deerflow/agents/checkpointer/async_provider.py:make_checkpointer"
+    "path": "./packages/harness/deerflow/runtime/checkpointer/async_provider.py:make_checkpointer"
   }
 }