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/backend/README.md

@@ -0,0 +1,5 @@
+# Winter CMS - Backend Module
+
+This repository is a read-only sub-split of the Winter CMS `Backend` module for use in Composer. Please note that we do not accept any pull requests to this repository.
+
+If you wish to make changes to this module, please submit them to the [main repository](https://github.com/wintercms/winter).