- Split the single expand button into two distinct buttons (expand /
  collapse), each with a chevron icon (fas fa-chevron-down /
  fas fa-chevron-up), shown or hidden via CSS classes.
- Add a new admin setting `facet_limit_collapse_label` to configure
  the label of the collapse button (like the existing
  `facet_limit_expand_label`)
- Add a "Reset all filters" button (#reset-facets) in faceted filtering
  mode that clears all active facet parameters from the URL
- Fix checkbox value attribute in facet-link.phtml: was incorrectly set
  to $name instead of $value
- Fix submitFacets(): also delete the page parameter when applying
  facets, and refactor facet-name detection into reusable helper
  functions (getVisibleFacetNames, isVisibleFacetParam)
- Minor code style harmonisation (single quotes to double quotes,
  spacing)