feat: show log indices on OpenSearch admin page

Add prefix query parameter to /admin/opensearch/indices endpoint so
the UI can fetch execution and log indices separately. OpenSearch admin
page now shows two card sections: Execution Indices and Log Indices,
each with doc count and size summary. Page restyled with CSS module
replacing inline styles. Delete endpoint also allows log index deletion.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/api/queries/admin/opensearch.ts

@@ -71,13 +71,14 @@ export function usePipelineStats() {
   });
 }
 
-export function useOpenSearchIndices(page = 0, size = 20, search = '') {
+export function useOpenSearchIndices(page = 0, size = 20, search = '', prefix = 'executions') {
   return useQuery({
-    queryKey: ['admin', 'opensearch', 'indices', page, size, search],
+    queryKey: ['admin', 'opensearch', 'indices', prefix, page, size, search],
     queryFn: () => {
       const params = new URLSearchParams();
       params.set('page', String(page));
       params.set('size', String(size));
+      params.set('prefix', prefix);
       if (search) params.set('search', search);
       return adminFetch<IndicesPage>(`/opensearch/indices?${params}`);
     },