feat: [sales] sales_products에 최저 개발비/구독료 컬럼 추가

- min_development_fee: 상품별 최저 개발비
- min_subscription_fee: 상품별 최저 구독료

database/migrations/2026_03_14_100001_add_min_fees_to_sales_products_table.php

@@ -0,0 +1,33 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    protected $connection = 'codebridge';
+
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::connection('codebridge')->table('sales_products', function (Blueprint $table) {
+            $table->decimal('min_development_fee', 15, 2)->default(0)->after('subscription_fee')
+                ->comment('최저 개발비 (이 금액 이하로 절대 불가)');
+            $table->decimal('min_subscription_fee', 15, 2)->default(0)->after('min_development_fee')
+                ->comment('최저 구독료 (이 금액 이하로 절대 불가)');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::connection('codebridge')->table('sales_products', function (Blueprint $table) {
+            $table->dropColumn(['min_development_fee', 'min_subscription_fee']);
+        });
+    }
+};