feat: add admin pinned messages section

- API client with full CRUD, broadcast, activate/deactivate, unpin endpoints
- List page with active/inactive badges, action buttons, pagination
- Create/edit form with content editor, media upload, display settings toggles
- Routes and navigation in admin marketing group
- i18n translations for ru, en, fa, zh

src/locales/zh.json

@@ -649,7 +649,8 @@
       "remnawave": "RemnaWave",
       "users": "用户",
       "trafficUsage": "流量使用",
-      "updates": "更新"
+      "updates": "更新",
+      "pinnedMessages": "置顶消息"
     },
     "panel": {
       "title": "管理面板",
@@ -673,7 +674,8 @@
       "remnawaveDesc": "面板管理和统计",
       "usersDesc": "管理机器人用户",
       "trafficUsageDesc": "按节点统计用户流量",
-      "updatesDesc": "机器人和面板版本"
+      "updatesDesc": "机器人和面板版本",
+      "pinnedMessagesDesc": "管理用户置顶消息"
     },
     "trafficUsage": {
       "title": "流量使用",
@@ -913,6 +915,48 @@
       "bothCreated": "群发已创建",
       "atLeastOneChannel": "请至少选择一个渠道"
     },
+    "pinnedMessages": {
+      "title": "置顶消息",
+      "subtitle": "管理用户置顶消息",
+      "create": "创建",
+      "empty": "暂无置顶消息",
+      "content": "消息文本",
+      "contentPlaceholder": "输入置顶消息文本...",
+      "noContent": "无文本",
+      "media": "媒体文件",
+      "addMedia": "添加媒体",
+      "uploading": "上传中...",
+      "settings": "设置",
+      "sendBeforeMenu": "菜单前发送",
+      "sendOnEveryStart": "每次启动时发送",
+      "broadcast": "广播",
+      "broadcastOnCreate": "创建时广播",
+      "broadcastConfirm": "向所有活跃用户广播置顶消息？",
+      "broadcastToAll": "广播给所有人",
+      "activate": "激活",
+      "deactivate": "停用",
+      "unpin": "取消置顶",
+      "unpinAll": "取消所有人的置顶",
+      "unpinConfirm": "取消所有用户的置顶消息？",
+      "delete": "删除",
+      "deleteConfirm": "删除此置顶消息？",
+      "active": "活跃",
+      "inactive": "不活跃",
+      "prev": "上一页",
+      "next": "下一页",
+      "createSuccess": "置顶消息已创建",
+      "updateSuccess": "消息已更新",
+      "deleteSuccess": "消息已删除",
+      "activateSuccess": "消息已激活",
+      "deactivateSuccess": "消息已停用",
+      "broadcastSuccess": "广播完成",
+      "unpinSuccess": "消息已取消置顶",
+      "sentCount": "已发送",
+      "failedCount": "失败",
+      "unpinnedCount": "已取消置顶",
+      "editMessage": "编辑",
+      "cantDeleteActive": "无法删除活跃消息"
+    },
     "settings": {
       "title": "系统设置",
       "allCategories": "所有分类",