Add menu item allergens, drop nav Help link, animate customizer price

- Menu items can now list allergens (shared catalog + join table),
  shown on the menu grid and item detail pages when applicable, and
  editable from the admin menu item form.
- Removed the top-nav "Help" link now that the footer links to it.
- The item customization page's price now uses the sliding
  AnimatedNumber, matching the basket line price.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/components/ordering/MenuList.module.scss

@@ -68,6 +68,12 @@
   color: $color-text-muted;
 }
 
+.allergens {
+  margin: $space-1 0 0;
+  font-size: 0.8rem;
+  color: $color-text-muted;
+}
+
 .quantity {
   display: flex;
   align-items: center;