feat(adminpanel): 任务监控「回收退款」手动兜底

新增 POST /api/admin/tasks/<id>/reap/:仅限卡在「已预留」超 10 分钟的僵尸任务(SUBMITTED/
POLLING 故意不许杀,视频合法耗时 5-10 分钟+,强杀会与轮询结算竞态),标失败 + 退还冻结积分,
与自动回收 _reap_stale_standalone_image_tasks 同款账务路径,幂等。

自动回收只在同团队下次提交时顺手触发,团队弃用某功能后冻结积分会永久躺着——这是给超管的
手动出口。序列化器加 reapable 字段(与端点闸同口径),任务监控行级「回收退款」按钮。
4 条测试(成功退款+审计/窗口内拒绝/非 RESERVED 拒绝/非超管 403)。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

core/backend/apps/adminpanel/urls.py

@@ -18,6 +18,7 @@ from .views import (
     admin_quota_policies,
     admin_quota_policy_detail,
     admin_task_detail,
+    admin_task_reap,
     admin_task_retry,
     admin_tasks,
     admin_prompt_template_detail,
@@ -55,6 +56,7 @@ urlpatterns = [
     path("tasks/", admin_tasks, name="admin-tasks"),
     path("tasks/<uuid:task_id>/", admin_task_detail, name="admin-task-detail"),
     path("tasks/<uuid:task_id>/retry/", admin_task_retry, name="admin-task-retry"),
+    path("tasks/<uuid:task_id>/reap/", admin_task_reap, name="admin-task-reap"),
     path("ledgers/", admin_ledgers, name="admin-ledgers"),
     path("ledgers/adjust/", admin_ledger_adjust, name="admin-ledger-adjust"),
     path("billing-config/", admin_billing_config, name="admin-billing-config"),