fix(admin/usage): 恢复成本 Tooltip 明细并优化账号筛选

问题修复:
- 恢复 Cost Tooltip 的成本分项明细 (input_cost, output_cost, cache 成本)
- 修复 Token Tooltip 双分隔线显示问题
- 修复 Tooltip 翻译键缺失问题，新增 costDetails/tokenDetails
- 恢复 Excel 导出格式化 (aoa_to_sheet + 翻译列头)

功能优化:
- 账号筛选从前端搜索改为后端搜索，避免一次加载 1000 条数据
- 行为与用户/API Key 筛选保持一致 (debounce + 后端分页)

frontend/src/views/admin/UsageView.vue

@@ -85,11 +85,48 @@ const exportToExcel = async () => {
       if (all.length >= total || res.items.length < 100) break; p++
     }
     if(!c.signal.aborted) {
-      // 动态加载 xlsx，降低首屏包体并减少高危依赖的常驻暴露面。
       const XLSX = await import('xlsx')
-      const ws = XLSX.utils.json_to_sheet(all); const wb = XLSX.utils.book_new(); XLSX.utils.book_append_sheet(wb, ws, 'Usage')
-      saveAs(new Blob([XLSX.write(wb, { bookType: 'xlsx', type: 'array' })], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' }), `usage_${Date.now()}.xlsx`)
-      appStore.showSuccess('Export Success')
+      const headers = [
+        t('usage.time'), t('admin.usage.user'), t('usage.apiKeyFilter'),
+        t('admin.usage.account'), t('usage.model'), t('admin.usage.group'),
+        t('usage.type'),
+        t('admin.usage.inputTokens'), t('admin.usage.outputTokens'),
+        t('admin.usage.cacheReadTokens'), t('admin.usage.cacheCreationTokens'),
+        t('admin.usage.inputCost'), t('admin.usage.outputCost'),
+        t('admin.usage.cacheReadCost'), t('admin.usage.cacheCreationCost'),
+        t('usage.rate'), t('usage.original'), t('usage.billed'),
+        t('usage.billingType'), t('usage.firstToken'), t('usage.duration'),
+        t('admin.usage.requestId')
+      ]
+      const rows = all.map(log => [
+        log.created_at,
+        log.user?.email || '',
+        log.api_key?.name || '',
+        log.account?.name || '',
+        log.model,
+        log.group?.name || '',
+        log.stream ? t('usage.stream') : t('usage.sync'),
+        log.input_tokens,
+        log.output_tokens,
+        log.cache_read_tokens,
+        log.cache_creation_tokens,
+        log.input_cost?.toFixed(6) || '0.000000',
+        log.output_cost?.toFixed(6) || '0.000000',
+        log.cache_read_cost?.toFixed(6) || '0.000000',
+        log.cache_creation_cost?.toFixed(6) || '0.000000',
+        log.rate_multiplier?.toFixed(2) || '1.00',
+        log.total_cost?.toFixed(6) || '0.000000',
+        log.actual_cost?.toFixed(6) || '0.000000',
+        log.billing_type === 1 ? t('usage.subscription') : t('usage.balance'),
+        log.first_token_ms ?? '',
+        log.duration_ms,
+        log.request_id || ''
+      ])
+      const ws = XLSX.utils.aoa_to_sheet([headers, ...rows])
+      const wb = XLSX.utils.book_new()
+      XLSX.utils.book_append_sheet(wb, ws, 'Usage')
+      saveAs(new Blob([XLSX.write(wb, { bookType: 'xlsx', type: 'array' })], { type: 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' }), `usage_${filters.value.start_date}_to_${filters.value.end_date}.xlsx`)
+      appStore.showSuccess(t('usage.exportSuccess'))
     }
   } catch (error) { console.error('Failed to export:', error); appStore.showError('Export Failed') }
   finally { if(exportAbortController === c) { exportAbortController = null; exporting.value = false; exportProgress.show = false } }

frontend/src/views/user/UsageView.vue

@@ -342,8 +342,8 @@
       >
         <div class="space-y-1.5">
           <!-- Token Breakdown -->
-          <div class="mb-2 border-b border-gray-700 pb-1.5">
-            <div class="text-xs font-semibold text-gray-300 mb-1">Token 明细</div>
+          <div>
+            <div class="text-xs font-semibold text-gray-300 mb-1">{{ t('usage.tokenDetails') }}</div>
             <div v-if="tokenTooltipData && tokenTooltipData.input_tokens > 0" class="flex items-center justify-between gap-4">
               <span class="text-gray-400">{{ t('admin.usage.inputTokens') }}</span>
               <span class="font-medium text-white">{{ tokenTooltipData.input_tokens.toLocaleString() }}</span>
@@ -389,6 +389,27 @@
         class="whitespace-nowrap rounded-lg border border-gray-700 bg-gray-900 px-3 py-2.5 text-xs text-white shadow-xl dark:border-gray-600 dark:bg-gray-800"
       >
         <div class="space-y-1.5">
+          <!-- Cost Breakdown -->
+          <div class="mb-2 border-b border-gray-700 pb-1.5">
+            <div class="text-xs font-semibold text-gray-300 mb-1">{{ t('usage.costDetails') }}</div>
+            <div v-if="tooltipData && tooltipData.input_cost > 0" class="flex items-center justify-between gap-4">
+              <span class="text-gray-400">{{ t('admin.usage.inputCost') }}</span>
+              <span class="font-medium text-white">${{ tooltipData.input_cost.toFixed(6) }}</span>
+            </div>
+            <div v-if="tooltipData && tooltipData.output_cost > 0" class="flex items-center justify-between gap-4">
+              <span class="text-gray-400">{{ t('admin.usage.outputCost') }}</span>
+              <span class="font-medium text-white">${{ tooltipData.output_cost.toFixed(6) }}</span>
+            </div>
+            <div v-if="tooltipData && tooltipData.cache_creation_cost > 0" class="flex items-center justify-between gap-4">
+              <span class="text-gray-400">{{ t('admin.usage.cacheCreationCost') }}</span>
+              <span class="font-medium text-white">${{ tooltipData.cache_creation_cost.toFixed(6) }}</span>
+            </div>
+            <div v-if="tooltipData && tooltipData.cache_read_cost > 0" class="flex items-center justify-between gap-4">
+              <span class="text-gray-400">{{ t('admin.usage.cacheReadCost') }}</span>
+              <span class="font-medium text-white">${{ tooltipData.cache_read_cost.toFixed(6) }}</span>
+            </div>
+          </div>
+          <!-- Rate and Summary -->
           <div class="flex items-center justify-between gap-6">
             <span class="text-gray-400">{{ t('usage.rate') }}</span>
             <span class="font-semibold text-blue-400"