feat: [수주관리] order_nodes 테이블 및 모델 생성 (N-depth 트리 구조)

- order_nodes 마이그레이션: 자기참조 parent_id, 고정코어(통계용) + options JSON(하이브리드)
- order_items에 order_node_id nullable FK 추가
- OrderNode 모델: BelongsToTenant, Auditable, SoftDeletes, 트리 관계(parent/children)
- Order 모델: nodes(), rootNodes() HasMany 관계 추가
- OrderItem 모델: order_node_id fillable + node() BelongsTo 관계 추가

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

database/migrations/2026_02_06_200000_create_order_nodes_table.php

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+<?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::create('order_nodes', function (Blueprint $table) {
+            $table->id()->comment('ID');
+            $table->foreignId('tenant_id')->comment('테넌트 ID');
+            $table->foreignId('order_id')->comment('수주 ID');
+
+            // ---- 트리 구조 ----
+            $table->foreignId('parent_id')->nullable()->comment('상위 노드 ID (NULL=루트)');
+
+            // ---- 고정 코어 (통계/집계용) ----
+            $table->string('node_type', 50)->comment('노드 유형 (location, zone, floor, room, process...)');
+            $table->string('code', 100)->comment('식별 코드');
+            $table->string('name', 200)->comment('표시명');
+            $table->string('status_code', 30)->default('PENDING')
+                ->comment('상태 (PENDING/CONFIRMED/IN_PRODUCTION/PRODUCED/SHIPPED/COMPLETED/CANCELLED)');
+            $table->integer('quantity')->default(1)->comment('수량');
+            $table->decimal('unit_price', 15, 2)->default(0)->comment('단가');
+            $table->decimal('total_price', 15, 2)->default(0)->comment('합계');
+
+            // ---- 유연 확장 (유형별 상세) ----
+            $table->json('options')->nullable()->comment('유형별 동적 속성 JSON');
+
+            // ---- 정렬 ----
+            $table->integer('depth')->default(0)->comment('트리 깊이 (0=루트)');
+            $table->integer('sort_order')->default(0)->comment('정렬 순서');
+
+            // ---- 감사 ----
+            $table->foreignId('created_by')->nullable()->comment('생성자 ID');
+            $table->foreignId('updated_by')->nullable()->comment('수정자 ID');
+            $table->foreignId('deleted_by')->nullable()->comment('삭제자 ID');
+            $table->timestamps();
+            $table->softDeletes();
+
+            // ---- 인덱스 ----
+            $table->index('tenant_id');
+            $table->index('parent_id');
+            $table->index(['order_id', 'depth', 'sort_order']);
+            $table->index(['order_id', 'node_type']);
+            $table->index(['tenant_id', 'node_type', 'status_code']); // 통계용
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('order_nodes');
+    }
+};

database/migrations/2026_02_06_200001_add_order_node_id_to_order_items_table.php

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+<?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('order_items', function (Blueprint $table) {
+            $table->foreignId('order_node_id')
+                ->nullable()
+                ->after('order_id')
+                ->comment('수주 노드 ID (order_nodes)');
+            $table->index('order_node_id');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('order_items', function (Blueprint $table) {
+            $table->dropIndex(['order_node_id']);
+            $table->dropColumn('order_node_id');
+        });
+    }
+};