feat:거래처 테이블에 매출/매입 구분(trade_type) 컬럼 추가

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

database/migrations/2026_02_13_160000_add_trade_type_to_trading_partners_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('trading_partners', function (Blueprint $table) {
+            $table->string('trade_type', 20)->default('sales')->after('name')->comment('매출/매입 구분 (sales/purchase)');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('trading_partners', function (Blueprint $table) {
+            $table->dropColumn('trade_type');
+        });
+    }
+};