Add extensive controller and model tests

tests/Feature/InstallerControllerTest.php

@@ -0,0 +1,23 @@
+<?php
+
+it('redirects installer when env exists', function (): void {
+    $response = $this->get('/install');
+
+    $response->assertRedirect('/');
+});
+
+it('blocks installer post when env exists', function (): void {
+    $response = $this->post('/install', [
+        'app_url' => 'https://example.com',
+        'db_host' => '127.0.0.1',
+        'db_port' => 3306,
+        'db_database' => 'test',
+        'db_username' => 'user',
+        'db_password' => 'pass',
+        'admin_name' => 'Admin',
+        'admin_email' => 'admin@example.com',
+        'admin_password' => 'Password123!',
+    ]);
+
+    $response->assertRedirect('/');
+});