feat: 新增管理员踢下线 VPN 客户端功能

- vpn/service.go: ClientInfo 增加 user_id 字段，新增 KickUser 方法
  用读锁收集目标连接后逐个关闭 WebSocket，返回断开数量
- vpn/tunnel.go: info() 填充 UserID
- handler/vpn.go: 新增 KickUserClient handler，校验用户存在后调用 KickUser
- router.go: 注册 DELETE /api/admin/vpn/clients/:id
- VpnView.vue: 在线客户端表格新增操作列与踢下线按钮，handleKick 确认后调用 API 并刷新
- zh.ts/en.ts: 新增 kick/confirmKick/kickFailed 国际化 key

frontend/src/views/VpnView.vue

@@ -18,6 +18,7 @@ interface Settings {
   do_remote_ip_config: boolean
 }
 interface ClientInfo {
+  user_id: number
   username: string
   ip: string
   ip6?: string
@@ -201,6 +202,21 @@ async function handleDeleteResv(id: number) {
   }
 }
 
+async function handleKick(userId: number, username: string) {
+  if (!confirm(t('vpn.confirmKick', { username }))) return
+  try {
+    const res = await fetch(`/api/admin/vpn/clients/${userId}`, {
+      method: 'DELETE',
+      headers: authHeader(),
+    })
+    const data = await res.json()
+    if (!res.ok) throw new Error(data.error || t('vpn.kickFailed'))
+    await fetchStatus()
+  } catch (e: any) {
+    error.value = e.message
+  }
+}
+
 function checkTunCreate(): boolean | null {
   if (!diag.value) return null
   return diag.value.tun_create.startsWith('ok')
@@ -425,17 +441,26 @@ onMounted(() => {
             <th class="px-6 py-3 text-left font-medium text-gray-500 dark:text-gray-400">{{ t('vpn.ipv4') }}</th>
             <th class="px-6 py-3 text-left font-medium text-gray-500 dark:text-gray-400">{{ t('vpn.ipv6') }}</th>
             <th class="px-6 py-3 text-left font-medium text-gray-500 dark:text-gray-400">{{ t('vpn.connectTime') }}</th>
+            <th class="px-6 py-3 text-left font-medium text-gray-500 dark:text-gray-400">{{ t('common.actions') }}</th>
           </tr>
         </thead>
         <tbody>
           <tr v-if="!status?.clients?.length">
-            <td colspan="4" class="px-6 py-6 text-center text-gray-400">{{ t('vpn.noOnlineClients') }}</td>
+            <td colspan="5" class="px-6 py-6 text-center text-gray-400">{{ t('vpn.noOnlineClients') }}</td>
           </tr>
           <tr v-for="(c, i) in status?.clients" :key="i" class="border-b border-gray-100 dark:border-gray-700/50">
             <td class="px-6 py-3 text-gray-900 dark:text-white font-medium">{{ c.username }}</td>
             <td class="px-6 py-3 text-gray-700 dark:text-gray-300">{{ c.ip }}</td>
             <td class="px-6 py-3 text-gray-700 dark:text-gray-300">{{ c.ip6 || '—' }}</td>
             <td class="px-6 py-3 text-gray-500 dark:text-gray-400">{{ c.connected_at }}</td>
+            <td class="px-6 py-3">
+              <button
+                class="px-3 py-1 text-xs rounded-md font-medium text-red-700 bg-red-50 hover:bg-red-100 dark:text-red-400 dark:bg-red-900/20 transition-colors"
+                @click="handleKick(c.user_id, c.username)"
+              >
+                {{ t('vpn.kick') }}
+              </button>
+            </td>
           </tr>
         </tbody>
       </table>