Add LangGraph-based agent orchestration implementation

backend/requirements-langgraph.txt

@@ -0,0 +1,18 @@
+# LangGraph and LangChain dependencies for agent orchestration
+langgraph==0.0.26
+langchain==0.1.8
+langchain-core==0.1.12
+langchain-ollama==0.1.0
+langchain-community==0.0.16
+
+# Core dependencies
+fastapi==0.109.0
+uvicorn==0.27.0
+sqlalchemy==2.0.23
+psycopg2-binary==2.9.9
+redis==5.0.1
+httpx==0.25.2
+pydantic==2.5.0
+
+# Additional utilities
+python-dotenv==1.0.0