feat(admin): 完善站点设置、内容回收站与后台菜单分组

新增站点设置与内容管理（含已删除恢复/清除），用户页改用独有运营指标，并按概览/内容/成员与经济/站点重组侧栏。

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

frontend/app/admin/settings/SettingsAdmin.tsx

@@ -0,0 +1,179 @@
+"use client";
+
+import { useState } from "react";
+import {
+  Globe,
+  Loader2,
+  Save,
+  UserPlus,
+} from "lucide-react";
+import {
+  apiUpdateSiteSettings,
+  type PublicSettings,
+} from "@/lib/api";
+import { toast } from "@/lib/toast";
+
+function Switch({
+  checked,
+  disabled,
+  onChange,
+  label,
+}: {
+  checked: boolean;
+  disabled?: boolean;
+  onChange: () => void;
+  label: string;
+}) {
+  return (
+    <button
+      type="button"
+      role="switch"
+      aria-checked={checked}
+      aria-label={label}
+      disabled={disabled}
+      onClick={onChange}
+      className="shrink-0 relative h-7 w-12 rounded-full transition-colors disabled:opacity-60"
+      style={{ background: checked ? "var(--accent)" : "var(--line-2)" }}
+    >
+      <span
+        className="absolute top-0.5 left-0.5 h-6 w-6 rounded-full bg-[var(--panel)] shadow transition-transform"
+        style={{ transform: checked ? "translateX(1.25rem)" : "translateX(0)" }}
+      />
+    </button>
+  );
+}
+
+export default function SettingsAdmin({ initial }: { initial: PublicSettings }) {
+  const [siteName, setSiteName] = useState(initial.site_name);
+  const [siteDescription, setSiteDescription] = useState(initial.site_description);
+  const [allowRegister, setAllowRegister] = useState(initial.allow_register);
+  const [savedName, setSavedName] = useState(initial.site_name);
+  const [savedDesc, setSavedDesc] = useState(initial.site_description);
+  const [saving, setSaving] = useState(false);
+  const [togglingReg, setTogglingReg] = useState(false);
+
+  const dirty =
+    siteName.trim() !== savedName || siteDescription.trim() !== savedDesc;
+
+  const saveIdentity = async () => {
+    if (saving) return;
+    const name = siteName.trim();
+    if (!name) {
+      toast("站点名称不能为空");
+      return;
+    }
+    setSaving(true);
+    try {
+      const res = await apiUpdateSiteSettings({
+        site_name: name,
+        site_description: siteDescription.trim(),
+      });
+      setSiteName(res.site_name);
+      setSiteDescription(res.site_description);
+      setSavedName(res.site_name);
+      setSavedDesc(res.site_description);
+      toast("站点信息已保存", "ok");
+    } catch (e) {
+      toast(e instanceof Error ? e.message : "保存失败");
+    } finally {
+      setSaving(false);
+    }
+  };
+
+  const toggleRegister = async () => {
+    if (togglingReg) return;
+    const next = !allowRegister;
+    setTogglingReg(true);
+    try {
+      const res = await apiUpdateSiteSettings({ allow_register: next });
+      setAllowRegister(res.allow_register);
+      toast(res.allow_register ? "已开放注册" : "已关闭注册", "ok");
+    } catch (e) {
+      toast(e instanceof Error ? e.message : "保存失败");
+    } finally {
+      setTogglingReg(false);
+    }
+  };
+
+  return (
+    <div className="max-w-3xl">
+      <div className="mb-5">
+        <h1
+          className="text-[22px] sm:text-[26px] font-extrabold tracking-tight flex items-center gap-2.5"
+          style={{ color: "var(--ink)" }}
+        >
+          <span
+            className="w-9 h-9 rounded-xl flex items-center justify-center"
+            style={{ background: "var(--accent-soft)", color: "var(--accent)" }}
+          >
+            <Globe size={18} />
+          </span>
+          站点设置
+        </h1>
+        <p className="meta mt-1.5 text-[12.5px]">
+          配置站点名称、简介与注册开关；主题色请到「外观」页调整
+        </p>
+      </div>
+
+      <section className="j13-module p-5 sm:p-6 mb-5">
+        <h2 className="text-[15px] font-semibold mb-1" style={{ color: "var(--ink)" }}>
+          基本信息
+        </h2>
+        <p className="meta text-[12.5px] mb-4">用于页眉品牌、页脚版权与 SEO 元信息</p>
+
+        <label className="field-label" htmlFor="site-name">
+          站点名称
+        </label>
+        <input
+          id="site-name"
+          className="field mb-4"
+          maxLength={32}
+          value={siteName}
+          onChange={(e) => setSiteName(e.target.value)}
+          placeholder="姜十三论坛"
+        />
+
+        <label className="field-label" htmlFor="site-desc">
+          站点简介
+        </label>
+        <textarea
+          id="site-desc"
+          className="field min-h-[96px] mb-4"
+          maxLength={160}
+          value={siteDescription}
+          onChange={(e) => setSiteDescription(e.target.value)}
+          placeholder="一句话介绍社区定位…"
+        />
+
+        <div className="flex justify-end">
+          <button
+            type="button"
+            className="btn btn-primary btn-sm"
+            disabled={!dirty || saving}
+            onClick={() => void saveIdentity()}
+          >
+            {saving ? <Loader2 size={14} className="animate-spin" /> : <Save size={14} />}
+            保存基本信息
+          </button>
+        </div>
+      </section>
+
+      <section className="j13-module p-5 sm:p-6 mb-5 flex items-start justify-between gap-4 flex-wrap">
+        <div className="min-w-0 flex-1">
+          <h2 className="text-[15px] font-semibold flex items-center gap-1.5" style={{ color: "var(--ink)" }}>
+            <UserPlus size={15} /> 开放注册
+          </h2>
+          <p className="meta text-[12.5px] mt-1 leading-relaxed">
+            关闭后，游客将无法提交注册；已有账号仍可登录。适用于内测或维护期。
+          </p>
+        </div>
+        <Switch
+          checked={allowRegister}
+          disabled={togglingReg}
+          onChange={() => void toggleRegister()}
+          label="开放注册"
+        />
+      </section>
+    </div>
+  );
+}

frontend/app/admin/settings/page.tsx

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+import type { Metadata } from "next";
+import { cookies } from "next/headers";
+import { getMeCached, getPublicSettingsCached } from "@/lib/serverData";
+import { authCookieHeader } from "@/lib/cookies";
+import { isSuperOrOwner } from "@/lib/roles";
+import Forbidden from "../Forbidden";
+import SettingsAdmin from "./SettingsAdmin";
+
+export const metadata: Metadata = {
+  title: "站点设置",
+};
+
+export default async function AdminSettingsPage() {
+  const cookie = authCookieHeader(await cookies());
+  const me = await getMeCached(cookie || undefined);
+  if (!me.user || !isSuperOrOwner(me.user.role)) {
+    return <Forbidden text="站点设置仅超级管理员和站长可操作。" />;
+  }
+  const settings = await getPublicSettingsCached();
+  return <SettingsAdmin initial={settings} />;
+}