fix: Memoize formatRelativeTime per thread item

- Wrap formatRelativeTime call in useMemo with thread.updatedAt dependency
- Prevents creating new Date() on every render for each thread item
- Improves thread list rendering performance

Fixes: #1100

surfsense_web/components/assistant-ui/thread-list.tsx

@@ -9,7 +9,7 @@ import {
 	TrashIcon,
 } from "lucide-react";
 import { useRouter } from "next/navigation";
-import { memo, useCallback, useEffect, useState } from "react";
+import { memo, useCallback, useEffect, useMemo, useState } from "react";
 import { Button } from "@/components/ui/button";
 import {
 	DropdownMenu,
@@ -237,7 +237,10 @@ const ThreadListItemComponent = memo(function ThreadListItemComponent({
 			<div className="flex-1 min-w-0">
 				<p className="truncate text-sm font-medium">{thread.title || "New Chat"}</p>
 				<p className="truncate text-xs text-muted-foreground">
-					{formatRelativeTime(new Date(thread.updatedAt))}
+					{useMemo(
+						() => formatRelativeTime(new Date(thread.updatedAt)),
+						[thread.updatedAt]
+					)}
 				</p>
 			</div>
 			<DropdownMenu>