fix: 审批流程三个bug修复

1. 点通过不再重复创建审批记录(后端无NULL记录时返回400而非自动创建)
2. 非提交人不再显示撤销按钮(列表页增加applicant_id校验)
3. 已审批工单不再显示通过/拒绝按钮(is_approver只计算pending记录)
4. 前端审批失败时弹出错误提示而非静默忽略

backend/internal/handler/ticket.go

@@ -138,7 +138,8 @@ func ListTickets(c *gin.Context) {
 		model.DB.Model(&model.TicketApproval{}).Where("ticket_id = ? AND step_type = 'execute'", t.ID).Count(&execCount)
 		var isExec, isAppr int64
 		model.DB.Model(&model.TicketApproval{}).Where("ticket_id = ? AND step_type = 'execute' AND approver_id = ?", t.ID, userID).Count(&isExec)
-		model.DB.Model(&model.TicketApproval{}).Where("ticket_id = ? AND step_type != 'execute' AND step_type != 'submit' AND approver_id = ?", t.ID, userID).Count(&isAppr)
+		// Only count PENDING approvals (action IS NULL) — already-approved records should not show approve button
+		model.DB.Model(&model.TicketApproval{}).Where("ticket_id = ? AND step_type != 'execute' AND step_type != 'submit' AND approver_id = ? AND action IS NULL", t.ID, userID).Count(&isAppr)
 		result = append(result, TicketWithMeta{
 			Ticket:         t,
 			HasAuditStep:   auditCount > 0,
@@ -496,24 +497,14 @@ func ApproveTicket(c *gin.Context) {
 
 	now := time.Now()
 
-	// Update approval record — auto-create if missing (legacy tickets)
+	// Find PENDING approval for this user (action IS NULL)
 	var approval model.TicketApproval
-	if err := model.DB.Where("ticket_id = ? AND approver_id = ? AND action IS NULL", id, userID).First(&approval).Error; err != nil {
-		// No approval record — authorized role can create one
-		stepName := "审核"
-		stepType := "audit"
-		approverRole := userRole
-		approval = model.TicketApproval{
-			TicketID:     ticket.ID,
-			StepNumber:   1,
-			StepName:     &stepName,
-			StepType:     &stepType,
-			ApproverID:   &userID,
-			ApproverRole: &approverRole,
-		}
-		model.DB.Create(&approval)
+	if err := model.DB.Where("ticket_id = ? AND approver_id = ? AND action IS NULL AND step_type != 'execute'", id, userID).First(&approval).Error; err != nil {
+		// Already approved or no pending approval for this user
+		c.JSON(http.StatusBadRequest, gin.H{"detail": "没有待处理的审批记录（你可能已经审批过了）"})
+		return
 	}
-	
+
 	approval.Action = &input.Action
 	approval.Comment = input.Comment
 	approval.ActualApproverID = &userID

frontend/src/pages/TicketsPage.tsx

@@ -6,7 +6,7 @@ import {
   ArrowUpDown, Ban, ChevronLeft, AlertTriangle,
 } from 'lucide-react';
 import { statusMap, statusColorMap, dbTypeColorMap } from '@/lib/constants';
-import { useActionPermission } from '@/hooks/useAuth';
+import { useActionPermission, useAuth } from '@/hooks/useAuth';
 import PageHeader from '@/components/PageHeader';
 import EmptyState from '@/components/EmptyState';
 import { ticketApi } from '@/api/ticket';
@@ -190,6 +190,7 @@ function TableRowSkeleton() {
 /* ------------------------------------------------------------------ */
 export default function TicketsPage() {
   const navigate = useNavigate();
+  const { user: currentUser } = useAuth();
   const canCreate = useActionPermission('ticket.create');
   const canApprove = useActionPermission('ticket.approve');
   const canExecute = useActionPermission('ticket.execute');
@@ -455,7 +456,10 @@ export default function TicketsPage() {
                                 try {
                                   await ticketApi.review(ticket.id, { action: 'approve', comment: '通过' });
                                   fetchTickets(); fetchStats();
-                                } catch { /* ignore */ }
+                                } catch (e: any) {
+                                  const msg = e?.response?.data?.detail || e?.message || '审批失败';
+                                  alert(msg);
+                                }
                               }}
                               className="dg-btn dg-btn-sm dg-btn-ghost text-green-400 hover:text-green-300"
                             >
@@ -470,7 +474,10 @@ export default function TicketsPage() {
                                 try {
                                   await ticketApi.review(ticket.id, { action: 'reject', comment: '拒绝' });
                                   fetchTickets(); fetchStats();
-                                } catch { /* ignore */ }
+                                } catch (e: any) {
+                                  const msg = e?.response?.data?.detail || e?.message || '操作失败';
+                                  alert(msg);
+                                }
                               }}
                               className="dg-btn dg-btn-sm dg-btn-ghost text-red-400 hover:text-red-300"
                             >
@@ -494,7 +501,7 @@ export default function TicketsPage() {
                             </button>
                           )}
 
-                          {(ticket.status === 'pending' || ticket.status === 'reviewing' || ticket.status === 'approved') && (
+                          {currentUser?.id === ticket.applicant_id && (ticket.status === 'pending' || ticket.status === 'reviewing' || ticket.status === 'approved') && (
                             <button
                               onClick={async () => {
                                 try {