feat(proxies): add account count column to proxy list

Display the number of accounts bound to each proxy in the admin proxy
management page, similar to the groups list view.

frontend/src/i18n/locales/en.ts

@@ -1561,6 +1561,7 @@ export default {
         protocol: 'Protocol',
         address: 'Address',
         status: 'Status',
+        accounts: 'Accounts',
         actions: 'Actions'
       },
       testConnection: 'Test Connection',

frontend/src/i18n/locales/zh.ts

@@ -1647,6 +1647,7 @@ export default {
         protocol: '协议',
         address: '地址',
         status: '状态',
+        accounts: '账号数',
         actions: '操作',
         nameLabel: '名称',
         namePlaceholder: '请输入代理名称',

frontend/src/views/admin/ProxiesView.vue

@@ -85,6 +85,14 @@
             </span>
           </template>
 
+          <template #cell-account_count="{ value }">
+            <span
+              class="inline-flex items-center rounded bg-gray-100 px-2 py-0.5 text-xs font-medium text-gray-800 dark:bg-dark-600 dark:text-gray-300"
+            >
+              {{ t('admin.groups.accountsCount', { count: value || 0 }) }}
+            </span>
+          </template>
+
           <template #cell-actions="{ row }">
             <div class="flex items-center gap-1">
               <button
@@ -534,6 +542,7 @@ const columns = computed<Column[]>(() => [
   { key: 'name', label: t('admin.proxies.columns.name'), sortable: true },
   { key: 'protocol', label: t('admin.proxies.columns.protocol'), sortable: true },
   { key: 'address', label: t('admin.proxies.columns.address'), sortable: false },
+  { key: 'account_count', label: t('admin.proxies.columns.accounts'), sortable: true },
   { key: 'status', label: t('admin.proxies.columns.status'), sortable: true },
   { key: 'actions', label: t('admin.proxies.columns.actions'), sortable: false }
 ])