migrations and models adjusted

database/migrations/2026_08_14_164132_create_rooms_table.php

@@ -15,6 +15,7 @@ return new class extends Migration
             $table->uuid('id')->primary();
             $table->string('title', 100)->nullable();
             $table->json('deck_config');
+            $table->string('join_code', 6)->unique();
             $table->unsignedInteger('current_round')->default(1);
             $table->timestamp('revealed_at')->nullable();
             $table->unsignedBigInteger('state_version')->default(1);