Add FastAPI backend with agent system

backend/app/models/base.py

@@ -0,0 +1,12 @@
+import uuid
+from datetime import datetime
+from sqlalchemy import Column, String, DateTime
+from app.database import Base
+
+
+class BaseModel(Base):
+    __abstract__ = True
+
+    id = Column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+    created_at = Column(DateTime, default=datetime.utcnow, nullable=False)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)