feat(admin): 分组管理列表新增用量列与账号数分类

分组管理列表增强：

1. 今日/累计用量列：
   - 新增独立端点 GET /admin/groups/usage-summary
   - 一次查询返回所有分组的今日费用和累计费用（actual_cost）
   - 前端异步加载后合并显示在分组列表中

2. 账号数区分可用/限流/总量：
   - 将账号数列从单一总量改为 badge 内多行展示
   - 可用: active + schedulable 的账号数（绿色）
   - 限流: rate_limit/overload/temp_unschedulable 的账号数（橙色，无限流时隐藏）
   - 总量: 全部关联账号数

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/views/admin/GroupsView.vue

@@ -158,12 +158,38 @@
             </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 #cell-account_count="{ row }">
+            <div class="space-y-0.5 text-xs">
+              <div>
+                <span class="text-gray-500 dark:text-gray-400">{{ t('admin.groups.accountsAvailable') }}</span>
+                <span class="ml-1 font-medium text-emerald-600 dark:text-emerald-400">{{ (row.active_account_count || 0) - (row.rate_limited_account_count || 0) }}</span>
+                <span class="ml-1 inline-flex items-center rounded bg-gray-100 px-1.5 py-0.5 font-medium text-gray-800 dark:bg-dark-600 dark:text-gray-300">{{ t('admin.groups.accountsUnit') }}</span>
+              </div>
+              <div v-if="row.rate_limited_account_count">
+                <span class="text-gray-500 dark:text-gray-400">{{ t('admin.groups.accountsRateLimited') }}</span>
+                <span class="ml-1 font-medium text-amber-600 dark:text-amber-400">{{ row.rate_limited_account_count }}</span>
+                <span class="ml-1 inline-flex items-center rounded bg-gray-100 px-1.5 py-0.5 font-medium text-gray-800 dark:bg-dark-600 dark:text-gray-300">{{ t('admin.groups.accountsUnit') }}</span>
+              </div>
+              <div>
+                <span class="text-gray-500 dark:text-gray-400">{{ t('admin.groups.accountsTotal') }}</span>
+                <span class="ml-1 font-medium text-gray-700 dark:text-gray-300">{{ row.account_count || 0 }}</span>
+                <span class="ml-1 inline-flex items-center rounded bg-gray-100 px-1.5 py-0.5 font-medium text-gray-800 dark:bg-dark-600 dark:text-gray-300">{{ t('admin.groups.accountsUnit') }}</span>
+              </div>
+            </div>
+          </template>
+
+          <template #cell-usage="{ row }">
+            <div v-if="usageLoading" class="text-xs text-gray-400">—</div>
+            <div v-else class="space-y-0.5 text-xs">
+              <div class="text-gray-500 dark:text-gray-400">
+                <span class="text-gray-400 dark:text-gray-500">{{ t('admin.groups.usageToday') }}</span>
+                <span class="ml-1 font-medium text-gray-700 dark:text-gray-300">${{ formatCost(usageMap.get(row.id)?.today_cost ?? 0) }}</span>
+              </div>
+              <div class="text-gray-500 dark:text-gray-400">
+                <span class="text-gray-400 dark:text-gray-500">{{ t('admin.groups.usageTotal') }}</span>
+                <span class="ml-1 font-medium text-gray-700 dark:text-gray-300">${{ formatCost(usageMap.get(row.id)?.total_cost ?? 0) }}</span>
+              </div>
+            </div>
           </template>
 
           <template #cell-status="{ value }">
@@ -1827,6 +1853,7 @@ const columns = computed<Column[]>(() => [
   { key: 'rate_multiplier', label: t('admin.groups.columns.rateMultiplier'), sortable: true },
   { key: 'is_exclusive', label: t('admin.groups.columns.type'), sortable: true },
   { key: 'account_count', label: t('admin.groups.columns.accounts'), sortable: true },
+  { key: 'usage', label: t('admin.groups.columns.usage'), sortable: false },
   { key: 'status', label: t('admin.groups.columns.status'), sortable: true },
   { key: 'actions', label: t('admin.groups.columns.actions'), sortable: false }
 ])
@@ -1963,6 +1990,8 @@ const copyAccountsGroupOptionsForEdit = computed(() => {
 
 const groups = ref<AdminGroup[]>([])
 const loading = ref(false)
+const usageMap = ref<Map<number, { today_cost: number; total_cost: number }>>(new Map())
+const usageLoading = ref(false)
 const searchQuery = ref('')
 const filters = reactive({
   platform: '',
@@ -2301,6 +2330,7 @@ const loadGroups = async () => {
     groups.value = response.items
     pagination.total = response.total
     pagination.pages = response.pages
+    loadUsageSummary()
   } catch (error: any) {
     if (signal.aborted || error?.name === 'AbortError' || error?.code === 'ERR_CANCELED') {
       return
@@ -2314,6 +2344,29 @@ const loadGroups = async () => {
   }
 }
 
+const formatCost = (cost: number): string => {
+  if (cost >= 1000) return cost.toFixed(0)
+  if (cost >= 100) return cost.toFixed(1)
+  return cost.toFixed(2)
+}
+
+const loadUsageSummary = async () => {
+  usageLoading.value = true
+  try {
+    const tz = Intl.DateTimeFormat().resolvedOptions().timeZone
+    const data = await adminAPI.groups.getUsageSummary(tz)
+    const map = new Map<number, { today_cost: number; total_cost: number }>()
+    for (const item of data) {
+      map.set(item.group_id, { today_cost: item.today_cost, total_cost: item.total_cost })
+    }
+    usageMap.value = map
+  } catch (error) {
+    console.error('Error loading group usage summary:', error)
+  } finally {
+    usageLoading.value = false
+  }
+}
+
 let searchTimeout: ReturnType<typeof setTimeout>
 const handleSearch = () => {
   clearTimeout(searchTimeout)