feat: welcome message, fix per_type save, add missing ciclos flows

- Show welcome_msg (button with "Ver menú") for all new sessions before category menu
- Fix saveConfig() AJAX to include per_type_menu DOM values so they survive individual saves
- Add welcome_menu field to General tab in admin (render + save)
- Add 'atras' command alias (→ show_main_menu)
- Add ciclos_plagas, ciclos_palm, ciclos_tratamientos flows to DB config
- Fix per_type in DB from [] to {} (proper JSON object)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/index.php

@@ -562,6 +562,8 @@ $routes = [
         }
         $approvalWebhook = trim($_POST['approval_webhook'] ?? '');
         if ($approvalWebhook !== '') $config['approval_webhook'] = $approvalWebhook;
+        $welcomeMenu = trim($_POST['welcome_menu'] ?? '');
+        if ($welcomeMenu !== '') $config['welcome_menu'] = $welcomeMenu;
 
         CompanyRepository::save(['id' => $companyId, 'config_json' => json_encode($config, JSON_UNESCAPED_UNICODE)]);
         header('Location: /admin/bot-config?id=' . $companyId . '&msg=saved');