Enhance edit button UX and align actions/creation section on /Admin route

Replace edit button with a checkmark in edit mode for better clarity. Improve alignment for actions column and footer create button.

Closes #147 (closed).

frontend/src/routes/admin/users/+page.svelte

 <script lang="ts">
 	import User from '$lib/types/user';
 	import { t } from '$lib/services/i18n';
-	import UserItem from '$lib/components/users/userItem.svelte';
+	import UserItem from './userItem.svelte';
 	import type { PageData } from './$types';
 
 	let { data }: { data: PageData } = $props();