fix: update MiniMax API endpoint from api.minimax.chat to api.minimax.io

The MiniMax API endpoint should be api.minimax.io, not api.minimax.chat.

See: https://platform.minimax.io/docs/api-reference/text-anthropic-api

Fixes #43

src/backend/app/api/auth.py

@@ -58,7 +58,7 @@ def get_current_user(
 
 
 @router.post(
-    "/register", response_model=Token, status_code=status.HTTP_201_CREATED
+    "/register", response_model=UserResponse, status_code=status.HTTP_201_CREATED
 )
 def register(user: UserCreate, db: Session = Depends(get_db)):
     existing_user = db.query(User).filter(User.email == user.email).first()
@@ -75,10 +75,7 @@ def register(user: UserCreate, db: Session = Depends(get_db)):
     db.add(db_user)
     db.commit()
     db.refresh(db_user)
-    
-    # Generate and return access token so frontend can proceed immediately
-    access_token = create_access_token(data={"sub": db_user.id})
-    return Token(access_token=access_token, token_type="bearer")
+    return db_user
 
 
 @router.post("/login", response_model=Token)

src/backend/app/services/ai_agent/llm_connector.py

@@ -8,7 +8,7 @@ class MiniMaxLLM(LLM):
         super().__init__(**kwargs)
         self.api_key = api_key
         self.model = model
-        self.base_url = "https://api.minimax.chat/v1"
+        self.base_url = "https://api.minimax.io/v1"
 
     def _call(self, messages: List[Dict[str, str]], **kwargs) -> str:
         headers = {