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

themes/demo/assets/vendor/bootstrap/less/responsive-embed.less

@@ -0,0 +1,35 @@
+// Embeds responsive
+//
+// Credit: Nicolas Gallagher and SUIT CSS.
+
+.embed-responsive {
+  position: relative;
+  display: block;
+  height: 0;
+  padding: 0;
+  overflow: hidden;
+
+  .embed-responsive-item,
+  iframe,
+  embed,
+  object,
+  video {
+    position: absolute;
+    top: 0;
+    left: 0;
+    bottom: 0;
+    height: 100%;
+    width: 100%;
+    border: 0;
+  }
+}
+
+// Modifier class for 16:9 aspect ratio
+.embed-responsive-16by9 {
+  padding-bottom: 56.25%;
+}
+
+// Modifier class for 4:3 aspect ratio
+.embed-responsive-4by3 {
+  padding-bottom: 75%;
+}