refactor: rename frontend/ to web-player/ and format with prettier

Updates the compose build context, the Dockerfile header, the package
name and the docs. The compose service and container keep the name
frontend/musify-frontend, since nginx routes to http://frontend:3000.

The source files also carry the first prettier pass, so the rename and
the reformat land together for them.

web-player/src/lib/components/ui/TrackTable.svelte

@@ -0,0 +1,39 @@
+<script lang="ts" module>
+	export const trackTableKey = Symbol('track-table');
+
+	export interface TrackTableContext {
+		readonly columns: string;
+	}
+</script>
+
+<script lang="ts">
+	import { setContext } from 'svelte';
+	import type { Snippet } from 'svelte';
+
+	interface Props {
+		columns: string;
+		class?: string;
+		headers: Snippet;
+		children: Snippet;
+	}
+
+	let { columns, class: klass = '', headers, children }: Props = $props();
+
+	setContext<TrackTableContext>(trackTableKey, {
+		get columns() {
+			return columns;
+		}
+	});
+</script>
+
+<div class={klass}>
+	<div
+		class="grid items-center gap-8 border-b border-line px-3 pb-2 text-sm font-medium tracking-wide text-muted uppercase"
+		style="grid-template-columns:{columns}"
+	>
+		{@render headers()}
+	</div>
+	<div class="mt-1 flex flex-col">
+		{@render children()}
+	</div>
+</div>