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/assets/less/layout/flexlayout.less

@@ -0,0 +1,50 @@
+.flex-layout-column {
+    .flex-display();
+    .flex-direction-column();
+
+    &.full-height-strict {
+        height: 100%;
+    }
+
+    &.absolute {
+        position: absolute!important;
+    }
+
+    &.fill-container {
+        position: absolute;
+        left: 0;
+        top: 0;
+        width: 100%;
+        height: 100%;
+    }
+}
+
+.flex-layout-row {
+    .flex-display();
+    .flex-direction-row();
+}
+
+.flex-layout-column, .flex-layout-row {
+    &.justify-center {.justify-content(center);}
+    &.align-center {
+        .align-items(center);
+        .align-content(center);
+    }
+
+    &.full-height {
+        min-height: 100%;
+        // height: 100%;
+    }
+}
+
+.flex-layout-item {
+    margin: 0;
+    &.fix { .flex-fix(); }
+    &.stretch { .flex-stretch(); }
+    &.stretch-constrain { .flex-stretch-constrain(); }
+    &.center { .align-self(center); }
+
+    &.relative { position: relative; }
+
+    &.layout-container { max-width: none; }
+}