feat(welcome): 站点外观 - 增加欢迎页开放开关并修复入口分包

web/src/services/api/welcome.ts

@@ -0,0 +1,5 @@
+import { http } from "./request";
+
+export function getWelcomeAvailability() {
+    return http.get<{ welcomeEnabled: boolean }>("/public/welcome");
+}