fix: calculate total file size on backend instead of frontend

- Backend returns total_size for all matching versions
- Frontend uses backend's total_size instead of computing from current page

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/pages/admin/versions/index.vue

@@ -68,9 +68,7 @@ const methodOptions = computed(() => [
   { label: t('admin.versions.methods.manual'), value: 'manual' },
 ])
 
-const totalSize = computed(() => {
-  return versions.value.reduce((sum, v) => sum + (v.file_size || 0), 0)
-})
+const totalSize = ref(0)
 
 const serverPagination = computed(() => ({
   page: currentPage.value,
@@ -131,6 +129,7 @@ async function fetchVersions() {
     versions.value = data?.versions || []
     total.value = data?.total || 0
     forcedCount.value = data?.forced_count || 0
+    totalSize.value = data?.total_size || 0
   }
   catch (error) {
     console.error('加载版本列表失败:', error)