enh: temp chat

deprecates chat history setting and introduces temp chat from model selector

src/lib/components/chat/Messages/Placeholder.svelte

@@ -2,7 +2,7 @@
 	import { WEBUI_BASE_URL } from '$lib/constants';
 	import { marked } from 'marked';
 
-	import { config, user, models as _models } from '$lib/stores';
+	import { config, user, models as _models, temporaryChatEnabled } from '$lib/stores';
 	import { onMount, getContext } from 'svelte';
 
 	import { blur, fade } from 'svelte/transition';
@@ -10,6 +10,7 @@
 	import Suggestions from '../MessageInput/Suggestions.svelte';
 	import { sanitizeResponseContent } from '$lib/utils';
 	import Tooltip from '$lib/components/common/Tooltip.svelte';
+	import EyeSlash from '$lib/components/icons/EyeSlash.svelte';
 
 	const i18n = getContext('i18n');
 
@@ -64,6 +65,18 @@
 			</div>
 		</div>
 
+		{#if $temporaryChatEnabled}
+			<Tooltip
+				content="This chat won't appear in history and your messages will not be saved."
+				className="w-fit"
+				placement="top-start"
+			>
+				<div class="flex items-center gap-2 text-gray-500 font-medium text-lg my-2 w-fit">
+					<EyeSlash strokeWidth="2.5" className="size-5" /> Temporary Chat
+				</div>
+			</Tooltip>
+		{/if}
+
 		<div
 			class=" mt-2 mb-4 text-3xl text-gray-800 dark:text-gray-100 font-semibold text-left flex items-center gap-4 font-primary"
 		>