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/traits/SelectableWidget.php

@@ -0,0 +1,69 @@
+<?php namespace Backend\Traits;
+
+use Input;
+
+/**
+ * Selectable Widget Trait
+ * Adds item selection features to back-end widgets
+ *
+ * @package winter\wn-backend-module
+ * @author Alexey Bobkov, Samuel Georges
+ */
+
+trait SelectableWidget
+{
+    protected $selectedItemsCache = false;
+
+    protected $selectionInputName = 'object';
+
+    public function onSelect()
+    {
+        $this->extendSelection();
+    }
+
+    protected function getSelectedItems()
+    {
+        if ($this->selectedItemsCache !== false) {
+            return $this->selectedItemsCache;
+        }
+
+        $items = $this->getSession('selected', []);
+        if (!is_array($items)) {
+            return $this->selectedItemsCache = [];
+        }
+
+        return $this->selectedItemsCache = $items;
+    }
+
+    protected function extendSelection()
+    {
+        $items = (array) Input::get($this->selectionInputName, []);
+        $currentSelection = $this->getSelectedItems();
+
+        $this->putSession('selected', $currentSelection + $items);
+    }
+
+    protected function resetSelection()
+    {
+        $this->putSession('selected', []);
+    }
+
+    protected function removeSelection($itemId)
+    {
+        $currentSelection = $this->getSelectedItems();
+
+        unset($currentSelection[$itemId]);
+        $this->putSession('selected', $currentSelection);
+        $this->selectedItemsCache = $currentSelection;
+    }
+
+    protected function isItemSelected($itemId)
+    {
+        $selectedItems = $this->getSelectedItems();
+        if (!is_array($selectedItems) || !isset($selectedItems[$itemId])) {
+            return false;
+        }
+
+        return $selectedItems[$itemId];
+    }
+}