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/services/apiV2.ts

@@ -39,6 +39,9 @@ import type {
   TranslationListResponse,
   TranslationResult,
   ExportRule,
+  StorageStats,
+  CleanupResult,
+  AdminTaskListResponse,
 } from '@/types/apiV2'
 
 /**
@@ -771,6 +774,48 @@ class ApiClientV2 {
   async deleteExportRule(ruleId: number): Promise<void> {
     await this.client.delete(`/export/rules/${ruleId}`)
   }
+
+  // ==================== Admin Storage Management ====================
+
+  /**
+   * Get storage statistics (admin only)
+   */
+  async getStorageStats(): Promise<StorageStats> {
+    const response = await this.client.get<StorageStats>('/admin/storage/stats')
+    return response.data
+  }
+
+  /**
+   * Trigger file cleanup (admin only)
+   */
+  async triggerCleanup(maxFilesPerUser?: number): Promise<CleanupResult> {
+    const params = maxFilesPerUser ? { max_files_per_user: maxFilesPerUser } : {}
+    const response = await this.client.post<CleanupResult>('/admin/cleanup/trigger', null, { params })
+    return response.data
+  }
+
+  /**
+   * List all tasks (admin only)
+   */
+  async listAllTasksAdmin(params: {
+    user_id?: number
+    status_filter?: string
+    include_deleted?: boolean
+    include_files_deleted?: boolean
+    page?: number
+    page_size?: number
+  }): Promise<AdminTaskListResponse> {
+    const response = await this.client.get<AdminTaskListResponse>('/admin/tasks', { params })
+    return response.data
+  }
+
+  /**
+   * Get task details (admin only, can view any task including deleted)
+   */
+  async getTaskAdmin(taskId: string): Promise<Task> {
+    const response = await this.client.get<Task>(`/admin/tasks/${taskId}`)
+    return response.data
+  }
 }
 
 // Export singleton instance