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/cms/controllers/themes/index.php

@@ -0,0 +1,11 @@
+<?= Block::put('body') ?>
+    <div class="layout">
+        <div class="layout-row">
+            <?= Form::open(['onsubmit'=>'return false']) ?>
+            <div class="layout theme-selector-layout" id="theme-list">
+                <?= $this->makePartial('theme_list') ?>
+            </div>
+            <?= Form::close() ?>
+        </div>
+    </div>
+<?= Block::endPut() ?>