fix(auth): allow registration without display name

apps/api/app/api/routes/auth.py

@@ -5,6 +5,8 @@ The route layer is intentionally thin: repository construction lives in
 app.dependencies and authentication behavior lives in application use cases.
 """
 
+from typing import Optional
+
 from app.auth import AuthenticatedUser, get_current_user
 from app.config import settings
 from app.dependencies import get_auth_email_service, get_auth_session_store, get_user_repository
@@ -32,7 +34,7 @@ class RegisterRequest(BaseModel):
     email: EmailStr
     password: str
     username: str
-    display_name: str
+    display_name: Optional[str] = None
 
 
 class RegisterResponse(BaseModel):
@@ -99,7 +101,7 @@ async def register(
             email=request.email,
             password=request.password,
             username=request.username,
-            display_name=request.display_name,
+            display_name=request.display_name or request.username,
         )
     )
     if error or response is None:

apps/web/src/pages/auth/Register.tsx

@@ -25,6 +25,7 @@ const Register: React.FC = () => {
         email: values.email,
         username: values.username,
         password: values.password,
+        display_name: values.username,
       });
       message.success('注册成功！请查收验证邮件。');
     } catch (error: any) {

tests/unit/test_auth.py

@@ -14,9 +14,11 @@ if str(API_ROOT) not in sys.path:
 
 from app.api.routes.auth import (
     PasswordResetRequestModel,
+    RegisterRequest,
     ResetPasswordModel,
     VerifyEmailRequestModel,
     forgot_password,
+    register,
     reset_password,
     verify_email_post,
 )
@@ -90,6 +92,21 @@ def test_register_use_case_hashes_password_and_normalizes_email():
     assert password_hasher.verify_password("Password1", user.password_hash)
 
 
+def test_register_route_defaults_display_name_to_username():
+    repo = InMemoryUserRepository()
+
+    response = asyncio.run(
+        register(
+            RegisterRequest(email="route@example.com", password="Password1", username="routeuser"),
+            repo,
+            DummyEmailService(),
+        )
+    )
+
+    assert response.display_name == "routeuser"
+    assert repo.find_by_email("route@example.com").display_name == "routeuser"
+
+
 def test_login_use_case_returns_verifiable_jwt():
     repo = InMemoryUserRepository()
     session_store = DummySessionStore()