feat: 统一管理端多语言、配置与票据/结算页面重构

src/lib/admin-locale.ts

@@ -100,15 +100,18 @@ export function applyAdminUiLocale(loc: AdminApiLocale): void {
 }
 
 /** 启动时从 localStorage 恢复（应在客户端尽早调用一次） */
-export function hydrateAdminUiLocale(): void {
+export function hydrateAdminUiLocale(): AdminApiLocale | null {
   if (typeof window === "undefined") {
-    return;
+    return null;
   }
   const stored = readStoredUiLocale();
   if (stored) {
     setAdminRequestLocale(stored);
     document.documentElement.lang = adminHtmlLang(stored);
+    return stored;
   }
+
+  return null;
 }
 
 /** 供 `admin-http`：`X-Locale` + `Accept-Language` */