perf(api,frontend): index hot queries, paginate chats, fix realtime

frontend/src/lib/components/search/SearchMessageItem.svelte

@@ -19,6 +19,7 @@
   const ownId = $derived(accounts.selected?.tg_user_id ?? null);
 
   $effect(() => {
+    chats.ensure(hit.chat_id);
     const ids: number[] = [];
     if (hit.chat_id > 0) {
       ids.push(hit.chat_id);