webui: add "Send message on Enter" setting (#21577)

* webui: make Enter to send chat a setting

* Shorten description

* Use isMobile hook from $lib/hooks

* Rebuild static output

tools/server/public/index.html

@@ -18,7 +18,7 @@
 		<div style="display: contents">
 			<script>
 				{
-					__sveltekit_6n4hpv = {
+					__sveltekit_1ao0o9h = {
 						base: new URL('.', location).pathname.slice(0, -1)
 					};