feat(dev): adopt shared platform-tools dev toolbar and one-click dev login

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

includes/dev_toolbar.php

@@ -0,0 +1,11 @@
+<?php
+// DEV ONLY -- barra de login de um clique (platform-tools). Não imprime nada
+// fora de dev. Incluída por includes/footer.php.
+require_once __DIR__ . '/../config/dev_guard.php';
+if (!function_exists('platform_dev_toolbar')) return;
+platform_dev_toolbar([
+    'login_url'  => base_url('dev_login'),
+    'logout_url' => base_url('views/auth/logout.php'),
+    'roles'      => ['admin' => 'Admin', 'sysadmin' => 'Sysadmin'],
+    'csrf_field' => 'csrf_field',
+]);