Fix/121 user list responsiveness

This MR addresses the issue where the user list wasn't responsive on smaller screens (look at the user list within a chat session):

• Toggle button is only displayed on short screen to display the user list
• the user list is now adapted for different screen sizes

Remark: There are other pages/components in the app that are not fully responsive yet.

frontend/src/routes/sessions/[id]/+page.svelte

@@ -52,7 +52,9 @@
 
 	<div
 		class="bg-white border rounded-lg shadow-md p-6 mx-4 my-2 h-fit w-full max-w-md text-base lg:text-lg"
-		class:!hidden={typeof window !== 'undefined' && !showParticipants && !window.matchMedia('(min-width: 1024px)').matches}
+		class:!hidden={typeof window !== 'undefined' &&
+			!showParticipants &&
+			!window.matchMedia('(min-width: 1024px)').matches}
 	>
 		<h2 class="text-xl truncate font-semibold text-gray-700 text-center mb-4">
 			{$t('utils.words.participants')}