feat: 后台增加开放消息开关

关闭后前台隐藏私聊/群聊入口并由后端拦截；同步去掉公告页重复计数胶囊。

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

frontend/app/admin/settings/SettingsAdmin.tsx

@@ -6,6 +6,7 @@ import {
   MessageSquare,
   Save,
   UserPlus,
+  MessagesSquare,
   ExternalLink,
   Shield,
   Mail,
@@ -107,12 +108,14 @@ export default function SettingsAdmin({ initial }: { initial: PublicSettings })
   const [siteDescription, setSiteDescription] = useState(initial.site_description);
   const [allowRegister, setAllowRegister] = useState(initial.allow_register);
   const [allowComments, setAllowComments] = useState(initial.allow_comments !== false);
+  const [allowMessages, setAllowMessages] = useState(initial.allow_messages !== false);
   const [postLinkNewTab, setPostLinkNewTab] = useState(initial.post_link_new_tab !== false);
   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 [togglingComments, setTogglingComments] = useState(false);
+  const [togglingMessages, setTogglingMessages] = useState(false);
   const [togglingLink, setTogglingLink] = useState(false);
   const [active, setActive] = useState<SectionId>("basic");
 
@@ -199,6 +202,21 @@ export default function SettingsAdmin({ initial }: { initial: PublicSettings })
     }
   };
 
+  const toggleMessages = async () => {
+    if (togglingMessages) return;
+    const next = !allowMessages;
+    setTogglingMessages(true);
+    try {
+      const res = await apiUpdateSiteSettings({ allow_messages: next });
+      setAllowMessages(res.allow_messages);
+      toast(res.allow_messages ? "已开放消息" : "已关闭消息", "ok");
+    } catch (e) {
+      toast(e instanceof Error ? e.message : "保存失败");
+    } finally {
+      setTogglingMessages(false);
+    }
+  };
+
   const togglePostLinkNewTab = async () => {
     if (togglingLink) return;
     const next = !postLinkNewTab;
@@ -293,7 +311,7 @@ export default function SettingsAdmin({ initial }: { initial: PublicSettings })
           </div>
 
           <div id="settings-content" className="scroll-mt-4">
-            <AdminSection title="内容与互动" description="控制注册、评论与链接打开方式">
+            <AdminSection title="内容与互动" description="控制注册、评论、消息与链接打开方式">
               <SwitchRow
                 bordered
                 title={
@@ -328,6 +346,23 @@ export default function SettingsAdmin({ initial }: { initial: PublicSettings })
                   />
                 }
               />
+              <SwitchRow
+                bordered
+                title={
+                  <>
+                    <MessagesSquare size={15} /> 开放消息
+                  </>
+                }
+                description="关闭后前台不展示私聊与群聊入口；已有会话由后台消息管理继续监管。"
+                control={
+                  <AdminSwitch
+                    checked={allowMessages}
+                    disabled={togglingMessages}
+                    onChange={() => void toggleMessages()}
+                    label="开放消息"
+                  />
+                }
+              />
               <SwitchRow
                 title={
                   <>