完善站点运营设置：分路由管理、登录可见评论、邮件模板内联与关闭注册 SSR。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/components/OperationalBanner.tsx

@@ -0,0 +1,17 @@
+"use client";
+import {useEffect,useState} from "react";
+import {usePathname} from "next/navigation";
+import {apiOperations} from "@/lib/api";
+export default function OperationalBanner(){
+ const path=usePathname();
+ const [notice,setNotice]=useState("");
+ useEffect(()=>{
+  let active=true;
+  const refresh=()=>{if(document.visibilityState!=="visible")return; void apiOperations<{maintenance:{mode:string;title:string;message:string}} >("/api/site-state").then(s=>{if(active)setNotice(s.maintenance.mode==="readonly" ? (s.maintenance.message || "站点暂时只读，可以浏览，暂不能提交或修改内容。") : "");}).catch(()=>{});};
+  refresh();const timer=setInterval(refresh,30000);
+  document.addEventListener("visibilitychange",refresh);
+  return ()=>{active=false;clearInterval(timer);document.removeEventListener("visibilitychange",refresh);};
+ },[path]);
+ if(path.startsWith("/admin") || !notice)return null;
+ return <div role="status" className="panel mx-auto my-3 w-full max-w-5xl p-4 text-sm"><strong>只读模式：</strong>{notice}</div>;
+}