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/services/memory_explicit_service.py

@@ -256,8 +256,10 @@ class MemoryExplicitService(MemoryBaseService):
                 s.content AS content,
                 s.created_at AS created_at
             ORDER BY s.created_at DESC
-            SKIP {skip} LIMIT {pagesize}
+            SKIP $skip LIMIT $limit
             """
+            params["skip"] = skip
+            params["limit"] = pagesize
 
             result = await self.neo4j_connector.execute_query(data_query, **params)