Refactor from Tailwind CSS to SCSS/Bootstrap

Major changes:
- Replace Tailwind with SCSS using Bootstrap-compatible variables
- Add Gulp build system for SCSS and JS compilation
- Split JS into modular partials (_events, _filters, _preview, etc.)

CSS fixes:
- Fix preview popover visibility (remove conflicting modal.scss rule)
- Fix search input max-width override for parent form styles
- Add filter panel styling (toggle buttons, chips, values row)
- Add group-body padding with negative margins on modifiers
- Style filter-group-toggle with eye icon for preview

JS additions:
- Add showGroupPreviewPopover for group count badge clicks
- Add showItemsPopover for rendering preview popover
- Add renderPreviewItems for product list rendering
- Add eye icon to filter toggle button generation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

sources/scss/layouts/_form-integration.scss

@@ -0,0 +1,81 @@
+/**
+ * Form Integration Styles
+ * Handles PrestaShop admin form layout overrides
+ */
+
+@use '../variables' as *;
+
+// Base border reset for all entity-selector elements
+.target-conditions-trait,
+.target-conditions-trait *,
+.entity-selector-trait,
+.entity-selector-trait *,
+.method-dropdown-menu,
+.method-dropdown-menu *,
+.target-preview-popover,
+.target-preview-popover * {
+    border-style: solid;
+    border-width: 0;
+    border-color: $es-border-color;
+}
+
+// Full-width form group override using :has()
+.form-group:has(.entity-selector-trait),
+.form-group:has(.target-conditions-trait),
+.form-group:has(.condition-trait) {
+    display: block;
+
+    > .control-label {
+        display: none;
+    }
+
+    > .col-lg-8 {
+        width: 100%;
+        max-width: 100%;
+        padding-left: $es-spacing-md;
+        padding-right: $es-spacing-md;
+        flex: 0 0 100% !important;
+    }
+}
+
+// Fallback class for browsers without :has() support
+.form-group.condition-trait-fullwidth {
+    display: block;
+
+    > .control-label {
+        display: none;
+    }
+
+    > .col-lg-8 {
+        width: 100%;
+        max-width: 100%;
+        padding-left: $es-spacing-md;
+        padding-right: $es-spacing-md;
+        flex: 0 0 100% !important;
+    }
+}
+
+// Dropdown overflow fix
+// When dropdown is open, parent containers must allow overflow
+.panel:has(.target-search-dropdown.show),
+.card:has(.target-search-dropdown.show),
+.form-wrapper:has(.target-search-dropdown.show),
+.panel-body:has(.target-search-dropdown.show),
+.card-body:has(.target-search-dropdown.show),
+.form-group:has(.target-search-dropdown.show),
+.col-lg-8:has(.target-search-dropdown.show),
+.col-lg-12:has(.target-search-dropdown.show) {
+    overflow: visible !important;
+}
+
+// Target conditions wrapper hierarchy overflow fix
+.target-conditions-trait:has(.target-search-dropdown.show),
+.entity-selector-trait:has(.target-search-dropdown.show),
+.condition-trait-body:has(.target-search-dropdown.show),
+.target-block-content:has(.target-search-dropdown.show),
+.target-block-groups:has(.target-search-dropdown.show),
+.target-group:has(.target-search-dropdown.show),
+.target-group-body:has(.target-search-dropdown.show),
+.target-search-wrapper:has(.target-search-dropdown.show) {
+    overflow: visible !important;
+}