feat:가입비(registration_fee) 컬럼 추가 및 시더 업데이트

database/migrations/2026_01_29_162847_add_registration_fee_to_sales_products_table.php

@@ -0,0 +1,32 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Support\Facades\DB;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('sales_products', function (Blueprint $table) {
+            $table->decimal('registration_fee', 15, 2)->default(0)->after('development_fee')->comment('가입비 (할인된 가격)');
+        });
+
+        // 기존 데이터: 가입비 = 개발비 × 25%
+        DB::statement('UPDATE sales_products SET registration_fee = development_fee * 0.25');
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('sales_products', function (Blueprint $table) {
+            $table->dropColumn('registration_fee');
+        });
+    }
+};