Categorize components/ui into primitives, overlay, media, forms and layout

Splits the flat 38-component ui/ folder into primitives/ (generic
controls), overlay/ (menus/modals), media/ (music-domain display
components), forms/ (composite entity forms) and layout/ (page
scaffolding), and updates every import path accordingly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web-player/src/lib/components/ui/primitives/Checkbox.svelte

@@ -0,0 +1,29 @@
+<script lang="ts">
+	import type { Snippet } from 'svelte';
+	import Check from '@lucide/svelte/icons/check';
+
+	interface Props {
+		checked?: boolean;
+		name?: string;
+		class?: string;
+		children: Snippet;
+	}
+
+	let { checked = $bindable(false), name, class: klass = '', children }: Props = $props();
+</script>
+
+<label class="flex items-center gap-3 text-sm text-fg-2 {klass}">
+	<span class="relative inline-grid size-5 shrink-0 place-items-center">
+		<input
+			type="checkbox"
+			{name}
+			bind:checked
+			class="peer size-5 cursor-pointer appearance-none rounded-tag border border-line bg-surface transition checked:border-accent-soft checked:bg-accent-soft focus-visible:border-accent/60 focus-visible:outline-none"
+		/>
+		<Check
+			class="pointer-events-none absolute size-3.5 text-ink opacity-0 transition peer-checked:opacity-100"
+			strokeWidth={3}
+		/>
+	</span>
+	<span class="cursor-pointer">{@render children()}</span>
+</label>