fix: stack tag filter and sort buttons vertically on mobile

Tags get full width for horizontal scrolling, sort buttons sit
below aligned to the right. Side by side on desktop.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/lib/components/NotesView.svelte

@@ -77,7 +77,7 @@
 {/if}
 
 {#if filter === 'all'}
-	<div class="mb-4 flex flex-wrap items-start justify-between gap-3">
+	<div class="mb-4 flex flex-col gap-3 md:flex-row md:items-start md:justify-between">
 		<TagFilter />
 		<SortSelector />
 	</div>