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/formwidgets/fieldset/assets/less/fieldset.less

@@ -0,0 +1,41 @@
+@import "../../../../assets/less/core/boot.less";
+
+@panel-bg: #f5f5f5;
+
+.fieldset {
+    position: relative;
+    min-height: 30px;
+
+    border: 1px solid @input-border;
+    border-radius: 0.5rem;
+    box-shadow: @input-box-shadow;
+
+    margin-top: 5px;
+    padding: 1em 1.25em 0 1.25em;
+
+    background: @panel-bg;
+
+    & > legend {
+        border: none;
+        margin: 0;
+        padding-inline: 1rem;
+        width: fit-content;
+        font-size: 18px;
+        color: inherit;
+    }
+    .control-tabs.primary-tabs {
+        .nav-tabs {
+            margin: 0;
+            > li.active > a:before {
+                background-color: @panel-bg;
+                border-color: @panel-bg;
+            }
+
+            > li > a > span.title {
+                &:before, &:after {
+                    background-color: @panel-bg;
+                }
+            }
+        }
+    }
+}