feat(api): Add user authentication functionality

- Implement JWT-based user authentication logic
- Add login endpoint and token validation middleware
- Update API routes with authentication dependencies
- Add authentication-related environment variables
- Optimize requirements.txt with necessary dependencies

lightrag/api/auth.py

@@ -0,0 +1,43 @@
+import os
+from datetime import datetime, timedelta
+import jwt
+from fastapi import HTTPException, status
+from pydantic import BaseModel
+
+
+class TokenPayload(BaseModel):
+    sub: str
+    exp: datetime
+
+
+class AuthHandler:
+    def __init__(self):
+        self.secret = os.getenv("TOKEN_SECRET", "4f85ds4f56dsf46")
+        self.algorithm = "HS256"
+        self.expire_hours = int(os.getenv("TOKEN_EXPIRE_HOURS", 4))
+
+    def create_token(self, username: str) -> str:
+        expire = datetime.utcnow() + timedelta(hours=self.expire_hours)
+        payload = TokenPayload(sub=username, exp=expire)
+        return jwt.encode(payload.dict(), self.secret, algorithm=self.algorithm)
+
+    def validate_token(self, token: str) -> str:
+        try:
+            payload = jwt.decode(token, self.secret, algorithms=[self.algorithm])
+            expire_timestamp = payload["exp"]
+            expire_time = datetime.utcfromtimestamp(expire_timestamp)
+
+            if datetime.utcnow() > expire_time:
+                raise HTTPException(
+                    status_code=status.HTTP_401_UNAUTHORIZED,
+                    detail="Token expired"
+                )
+            return payload["sub"]
+        except jwt.PyJWTError:
+            raise HTTPException(
+                status_code=status.HTTP_401_UNAUTHORIZED,
+                detail="Invalid token"
+            )
+
+
+auth_handler = AuthHandler()