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/controls/alert.less

@@ -0,0 +1,37 @@
+//
+// Custom alerts (Based on Sweet Alert)
+// --------------------------------------------------
+
+.sweet-overlay {
+    background-color: @overlay-background;
+    z-index: @zindex-alert - 1;
+}
+
+.sweet-alert {
+    text-align: right;
+    border-radius: @border-radius-base;
+    .box-shadow(@popup-box-shadow);
+    z-index: @zindex-alert;
+
+    h2 {
+        word-break: break-word;
+        word-wrap: break-word;
+        max-height: 350px;
+        overflow-y: auto;
+
+        margin: 10px 0 17px 0;
+        color: #2b3e50;
+        text-align: left;
+        font-size: 15px;
+        line-height: 23px;
+    }
+
+    p {
+        margin: 0;
+    }
+
+    p.text-muted {
+        margin-bottom: 20px;
+        color: #555555;
+    }
+}