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.

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

@@ -0,0 +1,20 @@
+<script lang="ts">
+	import type { Snippet } from 'svelte';
+
+	interface Props {
+		tone?: 'neutral' | 'danger';
+		class?: string;
+		children: Snippet;
+	}
+
+	let { tone = 'neutral', class: klass = '', children }: Props = $props();
+
+	const tones = {
+		neutral: 'border-line bg-surface text-fg-2',
+		danger: 'border-danger/20 bg-danger/10 text-danger-fg'
+	};
+</script>
+
+<p class="rounded-control border px-4 py-3 text-sm backdrop-blur-md {tones[tone]} {klass}">
+	{@render children()}
+</p>