feat: update frontend to work with v2 backend — camelCase, new endpoints, nested author

thoughts-frontend/app/users/[username]/followers/page.tsx

@@ -26,7 +26,7 @@ export default async function FollowersPage({ params }: FollowersPageProps) {
         <p className="text-muted-foreground">Users following @{username}.</p>
       </header>
       <main>
-        <UserListCard users={followersData.users} />
+        <UserListCard users={followersData.items} />
       </main>
     </div>
   );