Add clickable preview popover to filter group toggles

- Add showFilterGroupPreviewPopover method in _preview.js
- Make toggle-count badges clickable with data attributes
- Add event binding for .toggle-count.clickable in _events.js
- Add hover/active/loading styles for clickable toggle-count
- Requires previewFilterGroupProducts AJAX handler in PHP backend

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

sources/scss/components/_dropdown.scss

@@ -1242,6 +1242,38 @@ body > .target-search-dropdown,
                 font-size: 10px;
                 color: $es-primary;
             }
+
+            // Clickable preview badge
+            &.clickable {
+                cursor: pointer;
+                padding: 0.125rem 0.25rem;
+                border-radius: $es-radius-sm;
+                transition: all $es-transition-fast;
+
+                &:hover {
+                    background: rgba($es-primary, 0.1);
+                    color: $es-primary;
+
+                    i {
+                        color: $es-primary;
+                    }
+                }
+
+                &.popover-open {
+                    background: $es-primary;
+                    color: $es-white;
+
+                    i {
+                        color: $es-white;
+                    }
+                }
+
+                &.loading {
+                    i {
+                        animation: spin 0.6s linear infinite;
+                    }
+                }
+            }
         }
     }