fix(frontend): sidebar chat is not button problem (#187)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

- **Refactor**
- The interactive sidebar element was updated to use a button for
clearer semantic meaning and improved accessibility.
- The visual styling and click functionality remain unchanged for the
end-user.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: pengyu <pengyuchen01@gmail.com>

Author: PengyuChen01

frontend/src/components/sidebar-item.tsx

@@ -83,7 +83,7 @@ function SideBarItemComponent({
   };
 
   return (
-    <div
+    <button
       className={cn(
         buttonVariants({
           variant,
@@ -159,7 +159,7 @@ function SideBarItemComponent({
           </DialogHeader>
         </DialogContent>
       </Dialog>
-    </div>
+    </button>
   );
 }