feat: VivesPOS landing on Winter CMS 1.2 — theme + plugin + Dockerfile

- Base: wintercms/winter branch 1.2 (full framework)
- Theme vivespos: Canvas 7 + Bootstrap 5 CDN, custom CSS
- Layout: deferred GTM/GA4 tracking, JSON-LD SoftwareApplication
- Partials: hero (offline-first), features, modes (offline/nube toggle),
  screenshots, pricing (3 planes), comparison, FAQ, CTA
- Plugin VivesPOS.Site with ContactForm
- Dockerfile: PHP 8.2 Apache, port 80, healthcheck
- Added winter/wn-pages, blog, sitemap, seo plugins
- Active theme set to vivespos

modules/system/controllers/MailPartials.php

@@ -0,0 +1,42 @@
+<?php namespace System\Controllers;
+
+use BackendMenu;
+use Backend\Classes\Controller;
+use System\Classes\SettingsManager;
+
+/**
+ * Mail partials controller
+ *
+ * @package winter\wn-system-module
+ * @author Alexey Bobkov, Samuel Georges
+ */
+class MailPartials extends Controller
+{
+    /**
+     * @var array Extensions implemented by this controller.
+     */
+    public $implement = [
+        \Backend\Behaviors\FormController::class,
+    ];
+
+    /**
+     * @var array Permissions required to view this page.
+     */
+    public $requiredPermissions = ['system.manage_mail_templates'];
+
+    /**
+     * Constructor.
+     */
+    public function __construct()
+    {
+        parent::__construct();
+
+        BackendMenu::setContext('Winter.System', 'system', 'settings');
+        SettingsManager::setContext('Winter.System', 'mail_templates');
+    }
+
+    public function formBeforeSave($model)
+    {
+        $model->is_custom = 1;
+    }
+}