零 Node 部署、超级管理员，并完善本地构建发布文档。

- FastAPI 单进程托管 frontend/dist，systemd 替代 PM2

- 超级管理员 admin、注册开关与用户管理

- README/DEPLOY/USAGE 说明：改代码须本地构建 dist 后 push，服务器 update.sh

- 提交 frontend/dist 与 build-frontend 脚本

backend/app/schemas/__init__.py

@@ -46,6 +46,46 @@ class RefreshRequest(BaseModel):
 class UserOut(BaseModel):
     id: UUID
     username: str
+    is_superuser: bool = False
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class PublicSettingsOut(BaseModel):
+    registration_enabled: bool
+
+
+class SystemSettingsOut(BaseModel):
+    registration_enabled: bool
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class SystemSettingsUpdate(BaseModel):
+    registration_enabled: bool | None = None
+
+
+class AdminProfileUpdate(BaseModel):
+    username: str | None = Field(default=None, min_length=3, max_length=64)
+    current_password: str | None = None
+    password: str | None = Field(default=None, min_length=6, max_length=128)
+
+
+class AdminUserCreate(BaseModel):
+    username: str = Field(min_length=3, max_length=64)
+    password: str = Field(min_length=6, max_length=128)
+
+
+class AdminUserPasswordUpdate(BaseModel):
+    password: str = Field(min_length=6, max_length=128)
+
+
+class AdminUserOut(BaseModel):
+    id: UUID
+    username: str
+    is_superuser: bool
     created_at: datetime
 
     model_config = {"from_attributes": True}