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

database/migrations/2026_03_19_110000_add_approval_id_to_nonconforming_reports_table.php

@@ -0,0 +1,22 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('nonconforming_reports', function (Blueprint $table) {
+            $table->unsignedBigInteger('approval_id')->nullable()->after('status')->comment('결재 문서 ID');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('nonconforming_reports', function (Blueprint $table) {
+            $table->dropColumn('approval_id');
+        });
+    }
+};