feat: [품질관리] 백엔드 API 구현 - 품질관리서 + 실적신고

- 품질관리서(quality_documents) CRUD API 14개 엔드포인트
- 실적신고(performance_reports) 관리 API 6개 엔드포인트
- DB 마이그레이션 4개 테이블 (quality_documents, quality_document_orders, quality_document_locations, performance_reports)
- 모델 4개 + 서비스 2개 + 컨트롤러 2개 + FormRequest 4개
- stats() ambiguous column 버그 수정 (JOIN 시 테이블 접두사 추가)
- missing() status_code 컬럼명/값 수정

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

app/Models/Qualitys/QualityDocumentOrder.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace App\Models\Qualitys;
+
+use App\Models\Orders\Order;
+use Illuminate\Database\Eloquent\Model;
+
+class QualityDocumentOrder extends Model
+{
+    protected $table = 'quality_document_orders';
+
+    protected $fillable = [
+        'quality_document_id',
+        'order_id',
+    ];
+
+    public function qualityDocument()
+    {
+        return $this->belongsTo(QualityDocument::class);
+    }
+
+    public function order()
+    {
+        return $this->belongsTo(Order::class);
+    }
+
+    public function locations()
+    {
+        return $this->hasMany(QualityDocumentLocation::class);
+    }
+}