refactor(templates): fix admin sidebar navigation link

Update admin dashboard sidebar to point to user administration page
instead of profile settings:
- Change link from /profile to /admin/users
- Update label from 'Profile Settings' to 'User Administration'

This completes the admin navigation refactoring to use dedicated
admin pages instead of the main user profile page.

templates/admin.templ

@@ -21,8 +21,8 @@ templ Admin(user User) {
                         <a href="/admin" class="block px-4 py-2 rounded-lg bg-accent text-bg-primary" style="color: var(--text-primary)">
                             🏠 Dashboard
                         </a>
-<a href="/profile" class="block px-4 py-2 rounded-lg hover:opacity-80" style="color: var(--text-primary)">
-							👤 Profile Settings
+                        <a href="/admin/users" class="block px-4 py-2 rounded-lg hover:opacity-80" style="color: var(--text-primary)">
+							👤 User Administration
 						</a>
                         <a href="/admin/library" class="block px-4 py-2 rounded-lg hover:opacity-80" style="color: var(--text-primary)">
                             📚 Library Management