feat: unified preview eye icon component, enhanced search & preview

- Unify filter group and filter value preview icons into shared
  .filter-chip-wrapper + .chip-preview-btn component pattern
- Remove old .toggle-count.clickable inline eye icon approach
- Add dropdown-level event handler for preview buttons (dropdown
  appended to body, needs separate delegation)
- Enhanced EntitySearchEngine with improved product condition
  resolution and preview data
- Add EntityPreviewHandler for richer preview popovers
- Various SCSS improvements for chips, groups, and list-preview

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sources/scss/components/_chips.scss

@@ -343,6 +343,16 @@
         word-break: break-word;
     }
 
+    .chip-attrs {
+        font-size: 0.85em;
+        opacity: 0.7;
+        margin-left: 2px;
+
+        &::before {
+            content: '— ';
+        }
+    }
+
     .chip-remove {
         @include button-reset;
         display: flex;