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/partials/explain/plugins.htm

@@ -0,0 +1,17 @@
+<hr />
+
+<p class="lead">
+    <i class="icon-copy"></i> &nbsp; The HTML markup for this example:
+</p>
+<pre>
+{% apply escape %}
+{{ "{% component 'demoTodo' %}" }}
+{% endapply %}</pre>
+
+<hr />
+
+<p class="lead">
+    <i class="icon-question"></i> &nbsp; Wait, only one line is needed?
+</p>
+<p><em>Yes!</em> unlike the <a href="{{ 'ajax'|page }}">AJAX example</a>, components are simple building blocks that can be used with a small amount of code.</p>
+<p>The <code>demoTodo</code> component used here is provided by the plugin called <strong>Winter\Demo</strong>, you can find it in the <code>plugins/winter/demo</code> folder.</p>