fix: 完善审批流程调试日志

添加详细的调试日志来追踪审批流程：
1. approve() 方法开始时的参数日志
2. 节点类型和完成状态的日志
3. 下一节点查询和跳过逻辑的日志

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/service/BusinessTripService.php

@@ -682,6 +682,8 @@ class BusinessTripService
      */
     public function approve(int $userId, int $businessTripId, string $action, string $comment = ''): BusinessTrip
     {
+        error_log("📝 approve() 开始: userId={$userId}, businessTripId={$businessTripId}, action={$action}");
+
         return $this->db->transaction(function () use ($userId, $businessTripId, $action, $comment) {
             $businessTrip = BusinessTrip::with(['itineraries', 'approvalOrder'])->findOrFail($businessTripId);
 
@@ -744,22 +746,28 @@ class BusinessTripService
             // 更新审批单状态
             if ($action === 'reject') {
                 // 拒绝：直接结束流程
+                error_log("❌ 审批拒绝，结束流程");
                 $approvalOrder->status = ApprovalOrder::STATUS_REJECTED;
                 $approvalOrder->current_nodes = [];
                 $businessTrip->status = BusinessTrip::STATUS_REJECTED;
             } else {
+                error_log("✅ 审批同意，检查节点完成状态");
                 // 同意：检查当前节点是否完成，并处理流程流转
                 $nodeCompleted = false;
 
                 if ($currentNodeId) {
                     $node = ApprovalNode::find($currentNodeId);
+                    error_log("🔍 当前节点: id={$currentNodeId}, type=" . ($node ? $node->type : 'null'));
+
                     if ($node) {
                         // 根据节点类型判断是否完成
                         if ($node->type === 'approver') {
                             // 单人审批：一人通过即完成
+                            error_log("✅ 单人审批节点，一人通过即完成");
                             $nodeCompleted = true;
                         } elseif ($node->type === 'or_approve') {
                             // 或签：一人通过即完成
+                            error_log("✅ 或签节点，一人通过即完成");
                             $nodeCompleted = true;
                         } elseif ($node->type === 'and_approve') {
                             // 会签：需要所有人都通过
@@ -767,6 +775,7 @@ class BusinessTripService
                                 ->where('node_id', $currentNodeId)
                                 ->where('action', 'approve')
                                 ->count();
+                            error_log("🔍 会签节点: approvedCount={$approvedCount}, totalApprovers=" . count($approverIds));
                             if ($approvedCount >= count($approverIds)) {
                                 $nodeCompleted = true;
                             }
@@ -774,6 +783,8 @@ class BusinessTripService
                     }
                 }
 
+                error_log("🔍 nodeCompleted: " . ($nodeCompleted ? 'true' : 'false'));
+
                 if ($nodeCompleted) {
                     // 当前节点完成，查找下一个节点
                     error_log("✅ 节点 {$currentNodeId} 已完成，查找下一节点");