fix(ticket): implicit executor for default-flow tickets

- list is_executor and ExecuteTicket both required an execute-step
  approval record; tickets created without a workflow (default flow)
  had none, so the execute button never appeared and the API returned
  403 for everyone - admin/dba are now implicit executors (approved
  status only, consistent in both list enrichment and execution check)
- status labels: pending/reviewing/approved were all shown as 审核中;
  now 待初审/审批中/待执行 so the ready-to-execute state is visible
- verified end-to-end on test backend: create -> quick review dialog
  with comment -> impact-summary execute confirm -> success, detail
  page stage steps reach 完成 with execute result visible

frontend/src/features/ticket/constants.ts

@@ -5,9 +5,9 @@
 
 /** 展示用状态映射 — 按用户要求简化 */
 export const displayStatusMap: Record<string, string> = {
-  pending: '审核中',
-  reviewing: '审核中',
-  approved: '审核中',
+  pending: '待初审',
+  reviewing: '审批中',
+  approved: '待执行',
   rejected: '已拒绝',
   executing: '执行中',
   success: '完成',