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/core/mixins.less

@@ -0,0 +1,165 @@
+// --------------------------------------------------
+// Flexbox LESS mixins
+// The spec: http://www.w3.org/TR/css3-flexbox
+// --------------------------------------------------
+
+// Flexbox display
+// flex or inline-flex
+.flex-display() {
+    display: ~"-webkit-box";
+    display: ~"-webkit-flex";
+    display: ~"-moz-flex";
+    display: ~"-ms-flexbox"; // IE10 uses -ms-flexbox
+    display: ~"-ms-flex"; // IE11
+    display: flex;
+}
+
+// The 'flex: 0 0 auto' shorthand
+.flex-fix() {
+  -webkit-box-flex: 0;
+      -webkit-flex: 0 0 auto;
+         -moz-flex: 0 0 auto;
+          -ms-flex: 0 0 auto;
+              flex: 0 0 auto;
+}
+
+// The 'flex: 1 1 auto' shorthand
+.flex-stretch() {
+  -webkit-box-flex: 1;
+      -webkit-flex: 1 1 auto;
+         -moz-flex: 1 1 auto;
+          -ms-flex: 1 1 auto;
+              flex: 1 1 auto;
+}
+
+// The 'flex: 1' shorthand
+.flex-stretch-constrain() {
+  -webkit-box-flex: 1;
+      -webkit-flex: 1;
+         -moz-flex: 1;
+          -ms-flex: 1;
+              flex: 1;
+}
+
+// Flex Flow Direction Column
+// - applies to: flex containers
+.flex-direction-column() {
+  -webkit-flex-direction: column;
+     -moz-flex-direction: column;
+      -webkit-box-orient: vertical;
+      -ms-flex-direction: column;
+          flex-direction: column;
+}
+
+// Flex Flow Direction Row
+// - applies to: flex containers
+.flex-direction-row() {
+  -webkit-flex-direction: row;
+     -moz-flex-direction: row;
+      -webkit-box-orient: horizontal;
+      -ms-flex-direction: row;
+          flex-direction: row;
+}
+
+// Flex Line Wrapping
+// - applies to: flex containers
+// nowrap | wrap | wrap-reverse
+.flex-wrap(@wrap: nowrap) {
+  -webkit-flex-wrap: @wrap;
+     -moz-flex-wrap: @wrap;
+      -ms-flex-wrap: @wrap;
+          flex-wrap: @wrap;
+}
+
+// Flex Direction and Wrap
+// - applies to: flex containers
+// <flex-direction> || <flex-wrap>
+.flex-flow(@flow) {
+  -webkit-flex-flow: @flow;
+     -moz-flex-flow: @flow;
+      -ms-flex-flow: @flow;
+          flex-flow: @flow;
+}
+
+// Display Order
+// - applies to: flex items
+// <integer>
+.flex-order(@order: 0) {
+  -webkit-order: @order;
+     -moz-order: @order;
+      -ms-order: @order;
+          order: @order;
+}
+
+// Flex grow factor
+// - applies to: flex items
+// <number>
+.flex-grow(@grow: 0) {
+  -webkit-flex-grow: @grow;
+     -moz-flex-grow: @grow;
+      -ms-flex-grow: @grow;
+          flex-grow: @grow;
+}
+
+// Flex shr
+// - applies to: flex itemsink factor
+// <number> 
+.flex-shrink(@shrink: 1) {
+  -webkit-flex-shrink: @shrink;
+     -moz-flex-shrink: @shrink;
+      -ms-flex-shrink: @shrink;
+          flex-shrink: @shrink;
+}
+
+// Flex basis
+// - the initial main size of the flex item
+// - applies to: flex itemsnitial main size of the flex item
+// <width> 
+.flex-basis(@width: auto) {
+  -webkit-flex-basis: @width;
+     -moz-flex-basis: @width;
+      -ms-flex-basis: @width;
+          flex-basis: @width;
+}
+
+// Axis Alignment
+// - applies to: flex containers
+// flex-start | flex-end | center | space-between | space-around 
+.justify-content(@justify: flex-start) {
+  -webkit-justify-content: @justify;
+     -moz-justify-content: @justify;
+      -ms-justify-content: @justify;
+         -webkit-box-pack: @justify;
+          justify-content: @justify;
+}
+
+// Packing Flex Lines
+// - applies to: multi-line flex containers
+// flex-start | flex-end | center | space-between | space-around | stretch 
+.align-content(@align: stretch) {
+  -webkit-align-content: @align;
+     -moz-align-content: @align;
+      -webkit-box-align: @align;
+      -ms-align-content: @align;
+          align-content: @align;
+}
+
+// Cross-axis Alignment
+// - applies to: flex containers
+// flex-start | flex-end | center | baseline | stretch 
+.align-items(@align: stretch) {
+  -webkit-align-items: @align;
+     -moz-align-items: @align;
+      -ms-align-items: @align;
+          align-items: @align;
+}
+
+// Cross-axis Alignment
+// - applies to: flex items
+// auto | flex-start | flex-end | center | baseline | stretch 
+.align-self(@align: auto) {
+  -webkit-align-self: @align;
+     -moz-align-self: @align;
+      -ms-align-self: @align;
+          align-self: @align;
+}