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/NowPlaying.svelte

@@ -0,0 +1,25 @@
+<script lang="ts">
+	interface Props {
+		paused?: boolean;
+	}
+
+	let { paused = false }: Props = $props();
+
+	const bars = [
+		{ delay: 0, dur: 0.9 },
+		{ delay: 0.25, dur: 0.7 },
+		{ delay: 0.1, dur: 1.05 },
+		{ delay: 0.4, dur: 0.8 }
+	];
+</script>
+
+<div class="absolute inset-0 flex items-end justify-center gap-[2.5px] bg-black/45 pb-2">
+	{#each bars as bar, i (i)}
+		<span
+			class="w-[3px] origin-bottom rounded-full bg-white"
+			style="height:14px; animation:equalize {bar.dur}s ease-in-out {bar.delay}s infinite; animation-play-state:{paused
+				? 'paused'
+				: 'running'}"
+		></span>
+	{/each}
+</div>