ui: Constants refactor (#26908)

* refactor: Constants

* refactor: Constants/Enums cleanup

* refactor: Constant objects instead of multiple single value constants

* refactor: Cleanup constants

tools/ui/src/lib/components/app/chat/ChatScreen/ChatScreenActionScrollDown.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
 	import { ArrowDown } from '@lucide/svelte';
 	import ActionIcon from '$lib/components/app/actions/ActionIcon.svelte';
-	import { ICON_CLASS_DEFAULT } from '$lib/constants/css-classes';
+	import { ICON_CLASS_DEFAULT } from '$lib/constants';
 
 	let { onclick }: { onclick: (e?: MouseEvent) => void } = $props();
 </script>