Updates RBSearchView and adds the templates and CSS for the new faceted

search results page.
RBSearchView.dispatch now checks whether the active backend exposes

get_es_client. If it does, a FacetedSearchEngine is constructed and

_use_faceted is set to True. Any exception during construction falls back

silently to the existing Haystack path. Numeric queries still redirect directly

to the matching review request when accessible.
get_template_names returns search/results.html for the faceted path and

search/results_legacy.html for the Haystack path.
get_context_data on the faceted path calls FacetedSearchEngine.search,

builds the group sidebar items with total counts, resolves human-readable

labels for searchable filter buckets (reviewer, group, repository), and

assembles the filter panel context including current values, bucket lists, and

option counts.
results.html is the new template for the faceted path, providing the filter

sidebar and results list. results_legacy.html is the existing template

renamed, unchanged in behaviour.
search.less adds styles for the filter sidebar, bucket counts, active filter

indicators, and the Contents filter checkbox group.
_comment.html and _group.html are new partial templates for rendering

comment and group search results inline.

Verified that dispatch correctly routes to the faceted path when

Elasticsearch is available and falls back silently to the Haystack path when it

is not or when engine construction fails. Verified template selection, user

attachment on search hits, numeric query redirection, and Whoosh wildcard

rewriting. Confirmed the existing Haystack path is unaffected.