feat: 수주 관리 Phase 3 - 고급 기능 API 구현

- 견적→수주 변환 API (POST /orders/from-quote/{quoteId})
- 생산지시 생성 API (POST /orders/{id}/production-order)
- FormRequest 검증 클래스 추가
- 중복 생성 방지 및 상태 검증 로직

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

app/Http/Requests/Order/CreateProductionOrderRequest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace App\Http\Requests\Order;
+
+use App\Models\Production\WorkOrder;
+use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Validation\Rule;
+
+class CreateProductionOrderRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    public function rules(): array
+    {
+        return [
+            'process_type' => ['nullable', Rule::in(WorkOrder::PROCESS_TYPES)],
+            'assignee_id' => 'nullable|integer|exists:users,id',
+            'team_id' => 'nullable|integer|exists:departments,id',
+            'scheduled_date' => 'nullable|date',
+            'memo' => 'nullable|string',
+        ];
+    }
+
+    public function messages(): array
+    {
+        return [
+            'process_type.in' => __('validation.in', ['attribute' => '공정 유형']),
+            'assignee_id.exists' => __('validation.exists', ['attribute' => '담당자']),
+            'team_id.exists' => __('validation.exists', ['attribute' => '팀']),
+            'scheduled_date.date' => __('validation.date', ['attribute' => '예정일']),
+        ];
+    }
+}