feat: [material] 부적합관리 결재 연동 구현

- Migration: approval_id FK 추가
- Model: approval() BelongsTo 관계
- Service: submitForApproval() 결재상신 (결재문서+결재선 생성)
- ApprovalService: 승인→CLOSED, 반려/회수→approval_id 해제
- Controller: POST /{id}/submit-approval 엔드포인트
- Route: submit-approval 라우트 등록

app/Models/Materials/NonconformingReport.php

@@ -6,6 +6,7 @@
 use App\Models\Departments\Department;
 use App\Models\Items\Item;
 use App\Models\Orders\Order;
+use App\Models\Tenants\Approval;
 use App\Models\Users\User;
 use App\Traits\Auditable;
 use App\Traits\BelongsToTenant;
@@ -24,6 +25,7 @@ class NonconformingReport extends Model
         'tenant_id',
         'nc_number',
         'status',
+        'approval_id',
         'nc_type',
         'occurred_at',
         'confirmed_at',
@@ -104,6 +106,11 @@ public function items(): HasMany
         return $this->hasMany(NonconformingReportItem::class)->orderBy('sort_order');
     }
 
+    public function approval(): BelongsTo
+    {
+        return $this->belongsTo(Approval::class);
+    }
+
     public function order(): BelongsTo
     {
         return $this->belongsTo(Order::class);