feat(usage): 在 /admin/usage 支持查看已删除用户的历史使用情况

用户软删除后使用记录仍在,但身份(邮箱)被 ent 软删除拦截器隐藏。本次在
三条管理员只读路径定点穿透软删除过滤,并把删除状态传播到前端标记,零新表/
迁移/回填:

- 后端穿透:富化 usage 日志(loadUsers)、用户搜索(ListWithFilters +
  UserListFilters.IncludeDeleted)、点击详情(GetByIDIncludeDeleted /
  GetUserIncludeDeleted + getById ?include_deleted 分支)
- 状态传播:service.User / dto.User 新增 DeletedAt;SearchUsers 标记 deleted
- 前端:表格与余额弹窗展示"已删除"徽标、筛选下拉标注并排序、点击走
  include_deleted;新增 i18n admin.usage.userDeletedBadge
- 安全:普通用户 usage 仅查本人(无 PII 泄漏);主用户列表与默认 getById
  行为不变(已删用户仍 404);仅 admin 搜索设 IncludeDeleted

后端 build / 三态 vet / unit 全量 / 仓储集成全绿;前端 typecheck / vitest /
改动文件 eslint 全清。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/internal/server/api_contract_test.go

@@ -1492,6 +1492,10 @@ func (r *stubUserRepo) DisableTotp(ctx context.Context, userID int64) error {
 	return errors.New("not implemented")
 }
 
+func (r *stubUserRepo) GetByIDIncludeDeleted(ctx context.Context, id int64) (*service.User, error) {
+	panic("unexpected GetByIDIncludeDeleted call")
+}
+
 type stubApiKeyCache struct{}
 
 func (stubApiKeyCache) GetCreateAttemptCount(ctx context.Context, userID int64) (int, error) {

backend/internal/server/middleware/admin_auth_test.go

@@ -236,3 +236,7 @@ func (s *stubUserRepo) EnableTotp(ctx context.Context, userID int64) error {
 func (s *stubUserRepo) DisableTotp(ctx context.Context, userID int64) error {
 	panic("unexpected DisableTotp call")
 }
+
+func (s *stubUserRepo) GetByIDIncludeDeleted(ctx context.Context, id int64) (*service.User, error) {
+	panic("unexpected GetByIDIncludeDeleted call")
+}