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/calcresult.htm

@@ -0,0 +1,9 @@
+{% if result %}
+    <span class="lead">
+        The result is <span class="label label-success">{{ result }}</span>
+    </span>
+{% else %}
+    <span class="text-muted">
+        Click the <em>Calculate</em> button to find the answer.
+    </span>
+{% endif %}