删除数据库创建，唯一索引

database/migrations/2026_01_27_084640_create_admin_table.php

@@ -13,7 +13,7 @@ return new class extends Migration
     {
         Schema::create('admin_users', function (Blueprint $table) {
             $table->increments('id')->comment('管理用户ID');
-            $table->string('username', 190)->unique()->comment('登录账号');
+            $table->string('username', 190)->comment('登录账号');
             $table->string('password', 60)->comment('密码');
             $table->string('name')->comment('姓名');
             $table->string('avatar')->nullable()->comment('头像');