feat: 后端限速实现 + 前端i18n全面国际化 + 安全与代码质量修复

后端:
- trafficmgr: 实现 tc htb 限速（ApplyRateLimit/RemoveRateLimit），自动推导接口名
- 各协议服务: 代码质量改进与错误处理增强

前端:
- protocols.js: 170个硬编码中文字符串全部转为 i18n key，中英文双语翻译
- 提取 fmtBytes() 到 utils/format.js 公共模块（消除 4 处重复）
- router.js: 添加路由级权限守卫，非管理员无法直接 URL 访问管理页
- Tunnels.vue: SSE 日志流改用 fetch+ReadableStream，token 放 Authorization header
- VPNUsers.vue: 修复 catch 块中文硬编码 fallback
- 新增 TaskProgress 组件、taskmgr 后端任务管理

frontend/src/views/VPNUsers.vue

@@ -34,7 +34,7 @@
         </template>
       </el-table-column>
       <el-table-column :label="$t('common.traffic')" width="170">
-        <template #default="{ row }">{{ bytes(row.rx_bytes) }} / {{ bytes(row.tx_bytes) }}</template>
+        <template #default="{ row }">{{ fmtBytes(row.rx_bytes) }} / {{ fmtBytes(row.tx_bytes) }}</template>
       </el-table-column>
       <el-table-column :label="$t('vpnUsers.lastOnline')" width="180">
         <template #default="{ row }">{{ row.last_seen_at ? new Date(row.last_seen_at).toLocaleString() : '-' }}</template>
@@ -60,7 +60,7 @@
       <el-form-item :label="$t('vpnUsers.dialTunnel')" required>
         <el-select v-model="form.tunnel_id" style="width:100%" filterable>
           <el-option v-for="t in tunnels" :key="t.id" :value="t.id"
-            :label="`${t.name} (${protocolDisplay(t.protocol)})`" />
+            :label="`${t.name} (${$t(protocolDisplay(t.protocol))})`" />
         </el-select>
       </el-form-item>
       <el-form-item :label="$t('common.username')" required>
@@ -175,6 +175,7 @@ import { ElMessage, ElMessageBox } from 'element-plus'
 import { useI18n } from 'vue-i18n'
 import QRCode from 'qrcode'
 import api from '../api'
+import { fmtBytes } from '../utils/format'
 import { protocolDisplay } from '../protocols'
 
 const { t } = useI18n()
@@ -199,17 +200,10 @@ const mfaSaving = ref(false)
 const pinVisible = ref(false)
 const pinValue = ref('')
 
-const bytes = n => {
-  if (!n) return '0 B'
-  const u = ['B', 'KB', 'MB', 'GB', 'TB']
-  let i = 0
-  while (n >= 1024 && i < 4) { n /= 1024; i++ }
-  return `${n.toFixed(1)} ${u[i]}`
-}
 const tunnelName = id => tunnels.value.find(t => t.id === id)?.name || `#${id}`
 const tunnelProto = id => {
   const tun = tunnels.value.find(x => x.id === id)
-  return tun ? protocolDisplay(tun.protocol) : ''
+  return tun ? t(protocolDisplay(tun.protocol)) : ''
 }
 const isOpenVPN = id => tunnels.value.find(x => x.id === id)?.protocol === 'openvpn'
 const isLocked = row => row.mfa_locked_until && new Date(row.mfa_locked_until) > new Date()
@@ -259,14 +253,22 @@ async function create() {
 }
 
 async function toggle(row) {
-  await api.put(`/vpn-users/${row.id}`, { enabled: !row.enabled, display_name: row.display_name, email: row.email })
-  load()
+  try {
+    await api.put(`/vpn-users/${row.id}`, { enabled: !row.enabled, display_name: row.display_name, email: row.email })
+    load()
+  } catch (e) {
+    ElMessage.error(e.response?.data?.error || t('common.operationFailed'))
+  }
 }
 
 async function remove(row) {
-  await ElMessageBox.confirm(t('vpnUsers.deleteVpnUserConfirm', { username: row.username }), t('common.confirm'))
-  await api.delete(`/vpn-users/${row.id}`)
-  load()
+  try {
+    await ElMessageBox.confirm(t('vpnUsers.deleteVpnUserConfirm', { username: row.username }), t('common.confirm'))
+    await api.delete(`/vpn-users/${row.id}`)
+    load()
+  } catch (e) {
+    if (e !== 'cancel') ElMessage.error(e.response?.data?.error || t('common.deleteFailed'))
+  }
 }
 
 async function download(row) {
@@ -311,7 +313,7 @@ async function refreshOTPStatus() {
       mfa_locked: isLocked(otpUser.value),
       mfa_locked_until: otpUser.value.mfa_locked_until,
       mfa_last_used_at: otpUser.value.mfa_last_used_at,
-      compatible: 'TOTP 标准（兼容 Google/Microsoft Authenticator）'
+      compatible: t('vpnUsers.totpCompatible')
     }
   }
 }