feat: add storage cleanup mechanism with soft delete and auto scheduler

- Add soft delete (deleted_at column) to preserve task records for statistics
- Implement cleanup service to delete old files while keeping DB records
- Add automatic cleanup scheduler (configurable interval, default 24h)
- Add admin endpoints: storage stats, cleanup trigger, scheduler status
- Update task service with admin views (include deleted/files_deleted)
- Add frontend storage management UI in admin dashboard
- Add i18n translations for storage management

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/pages/AdminDashboardPage.tsx

@@ -7,7 +7,7 @@ import { useState, useEffect } from 'react'
 import { useNavigate } from 'react-router-dom'
 import { useTranslation } from 'react-i18next'
 import { apiClientV2 } from '@/services/apiV2'
-import type { SystemStats, UserWithStats, TopUser, TranslationStats } from '@/types/apiV2'
+import type { SystemStats, UserWithStats, TopUser, TranslationStats, StorageStats } from '@/types/apiV2'
 import {
   Users,
   ClipboardList,
@@ -21,6 +21,8 @@ import {
   Loader2,
   Languages,
   Coins,
+  HardDrive,
+  Trash2,
 } from 'lucide-react'
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
 import { Button } from '@/components/ui/button'
@@ -41,6 +43,8 @@ export default function AdminDashboardPage() {
   const [users, setUsers] = useState<UserWithStats[]>([])
   const [topUsers, setTopUsers] = useState<TopUser[]>([])
   const [translationStats, setTranslationStats] = useState<TranslationStats | null>(null)
+  const [storageStats, setStorageStats] = useState<StorageStats | null>(null)
+  const [cleanupLoading, setCleanupLoading] = useState(false)
   const [loading, setLoading] = useState(true)
   const [error, setError] = useState('')
 
@@ -50,17 +54,19 @@ export default function AdminDashboardPage() {
       setLoading(true)
       setError('')
 
-      const [statsData, usersData, topUsersData, translationStatsData] = await Promise.all([
+      const [statsData, usersData, topUsersData, translationStatsData, storageStatsData] = await Promise.all([
         apiClientV2.getSystemStats(),
         apiClientV2.listUsers({ page: 1, page_size: 10 }),
         apiClientV2.getTopUsers({ metric: 'tasks', limit: 5 }),
         apiClientV2.getTranslationStats(),
+        apiClientV2.getStorageStats(),
       ])
 
       setStats(statsData)
       setUsers(usersData.users)
       setTopUsers(topUsersData)
       setTranslationStats(translationStatsData)
+      setStorageStats(storageStatsData)
     } catch (err: any) {
       console.error('Failed to fetch admin data:', err)
       setError(err.response?.data?.detail || t('admin.loadFailed'))
@@ -80,6 +86,27 @@ export default function AdminDashboardPage() {
     return date.toLocaleString(i18n.language === 'zh-TW' ? 'zh-TW' : 'en-US')
   }
 
+  // Handle cleanup trigger
+  const handleCleanup = async () => {
+    try {
+      setCleanupLoading(true)
+      const result = await apiClientV2.triggerCleanup()
+      alert(t('admin.storage.cleanupResult', {
+        users: result.users_processed,
+        files: result.total_files_deleted,
+        mb: (result.total_bytes_freed / 1024 / 1024).toFixed(2)
+      }))
+      // Refresh storage stats
+      const newStorageStats = await apiClientV2.getStorageStats()
+      setStorageStats(newStorageStats)
+    } catch (err: any) {
+      console.error('Cleanup failed:', err)
+      alert(t('admin.storage.cleanupFailed'))
+    } finally {
+      setCleanupLoading(false)
+    }
+  }
+
   if (loading) {
     return (
       <div className="flex items-center justify-center min-h-screen">
@@ -329,6 +356,104 @@ export default function AdminDashboardPage() {
         </Card>
       )}
 
+      {/* Storage Management */}
+      {storageStats && (
+        <Card>
+          <CardHeader>
+            <div className="flex items-center justify-between">
+              <div>
+                <CardTitle className="flex items-center gap-2">
+                  <HardDrive className="w-5 h-5" />
+                  {t('admin.storage.title')}
+                </CardTitle>
+                <CardDescription>{t('admin.storage.description')}</CardDescription>
+              </div>
+              <Button
+                onClick={handleCleanup}
+                disabled={cleanupLoading}
+                variant="outline"
+                className="gap-2"
+              >
+                {cleanupLoading ? (
+                  <Loader2 className="w-4 h-4 animate-spin" />
+                ) : (
+                  <Trash2 className="w-4 h-4" />
+                )}
+                {t('admin.storage.triggerCleanup')}
+              </Button>
+            </div>
+          </CardHeader>
+          <CardContent>
+            <div className="grid grid-cols-1 md:grid-cols-4 gap-4 mb-6">
+              <div className="p-4 bg-blue-50 rounded-lg">
+                <div className="flex items-center gap-2 text-blue-600 mb-1">
+                  <ClipboardList className="w-4 h-4" />
+                  <span className="text-sm font-medium">{t('admin.storage.totalTasks')}</span>
+                </div>
+                <div className="text-2xl font-bold text-blue-700">
+                  {storageStats.total_tasks.toLocaleString()}
+                </div>
+              </div>
+
+              <div className="p-4 bg-green-50 rounded-lg">
+                <div className="flex items-center gap-2 text-green-600 mb-1">
+                  <CheckCircle2 className="w-4 h-4" />
+                  <span className="text-sm font-medium">{t('admin.storage.tasksWithFiles')}</span>
+                </div>
+                <div className="text-2xl font-bold text-green-700">
+                  {storageStats.tasks_with_files.toLocaleString()}
+                </div>
+              </div>
+
+              <div className="p-4 bg-amber-50 rounded-lg">
+                <div className="flex items-center gap-2 text-amber-600 mb-1">
+                  <Trash2 className="w-4 h-4" />
+                  <span className="text-sm font-medium">{t('admin.storage.filesDeleted')}</span>
+                </div>
+                <div className="text-2xl font-bold text-amber-700">
+                  {storageStats.tasks_files_deleted.toLocaleString()}
+                </div>
+              </div>
+
+              <div className="p-4 bg-gray-50 rounded-lg">
+                <div className="flex items-center gap-2 text-gray-600 mb-1">
+                  <XCircle className="w-4 h-4" />
+                  <span className="text-sm font-medium">{t('admin.storage.softDeleted')}</span>
+                </div>
+                <div className="text-2xl font-bold text-gray-700">
+                  {storageStats.soft_deleted_tasks.toLocaleString()}
+                </div>
+              </div>
+            </div>
+
+            {/* Disk Usage */}
+            <div className="border rounded-lg p-4">
+              <h4 className="text-sm font-medium text-gray-700 mb-3">{t('admin.storage.diskUsage')}</h4>
+              <div className="grid grid-cols-3 gap-4 text-center">
+                <div>
+                  <div className="text-lg font-semibold text-blue-600">
+                    {storageStats.disk_usage.uploads_mb} MB
+                  </div>
+                  <div className="text-xs text-gray-500">{t('admin.storage.uploadsSize')}</div>
+                </div>
+                <div>
+                  <div className="text-lg font-semibold text-green-600">
+                    {storageStats.disk_usage.results_mb} MB
+                  </div>
+                  <div className="text-xs text-gray-500">{t('admin.storage.resultsSize')}</div>
+                </div>
+                <div>
+                  <div className="text-lg font-semibold text-purple-600">
+                    {storageStats.disk_usage.total_mb} MB
+                  </div>
+                  <div className="text-xs text-gray-500">{t('admin.storage.totalSize')}</div>
+                </div>
+              </div>
+            </div>
+          </CardContent>
+        </Card>
+      )}
+
       {/* Top Users */}
       {topUsers.length > 0 && (
         <Card>