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/assets/js/mailbrandsettings/mailbrandsettings.js

@@ -0,0 +1,37 @@
+var previewIframe
+
+$(document).on('change', '.field-colorpicker', function() {
+    $('#brandSettingsForm').request('onUpdateSampleMessage').done(function(data) {
+        updatePreviewContent(data.previewHtml)
+    })
+})
+
+function updatePreviewContent(content) {
+    'srcdoc' in previewIframe
+        ? previewIframe.srcdoc = content
+        : previewIframe.src = 'data:text/html;charset=UTF-8,' + content
+}
+
+function adjustPreviewHeight() {
+    previewIframe.style.height = (previewIframe.contentWindow.document.getElementsByTagName('body')[0].scrollHeight) +'px'
+}
+
+function createPreviewContainer(el, content) {
+    previewIframe = document.createElement('iframe')
+
+    updatePreviewContent(content)
+
+    previewIframe.style.width = '100%'
+    previewIframe.setAttribute('frameborder', 0)
+    previewIframe.setAttribute('id', el.id)
+    previewIframe.onload = adjustPreviewHeight
+
+    var parent = el.parentNode
+    parent.replaceChild(previewIframe, el)
+
+    /*
+     * Auto adjust height
+     */
+    $(document).render(adjustPreviewHeight)
+    $(window).resize(adjustPreviewHeight)
+}