fix(memory): fix problems

- Parameterize SKIP/LIMIT in Cypher query instead of f-string interpolation
- Add UUID format validation in validate_end_user_in_workspace before DB query
- Update limit/depth Query descriptions to clarify auto-cap behavior in service layer
- Move uuid import to module level in api_key_utils.py

Modified files:
- api/app/services/memory_explicit_service.py
- api/app/core/api_key_utils.py
- api/app/controllers/service/user_memory_api_controller.py

api/app/controllers/service/user_memory_api_controller.py

@@ -44,8 +44,8 @@ async def get_graph_data(
     request: Request,
     end_user_id: str = Query(..., description="End user ID"),
     node_types: Optional[str] = Query(None, description="Comma-separated node types filter"),
-    limit: int = Query(100, description="Max nodes to return, capped at 1000"),
-    depth: int = Query(1, description="Graph traversal depth, capped at 3"),
+    limit: int = Query(100, description="Max nodes to return (auto-capped at 1000 in service layer)"),
+    depth: int = Query(1, description="Graph traversal depth (auto-capped at 3 in service layer)"),
     center_node_id: Optional[str] = Query(None, description="Center node for subgraph"),
     api_key_auth: ApiKeyAuth = None,
     db: Session = Depends(get_db),