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/routes/(app)/playlists/+page.svelte

@@ -0,0 +1,99 @@
+<script lang="ts">
+	import Plus from '@lucide/svelte/icons/plus';
+	import ListMusic from '@lucide/svelte/icons/list-music';
+	import Page from '$lib/components/ui/Page.svelte';
+	import PageHeader from '$lib/components/ui/PageHeader.svelte';
+	import MediaGrid from '$lib/components/ui/MediaGrid.svelte';
+	import PlaylistCard from '$lib/components/ui/PlaylistCard.svelte';
+	import Modal from '$lib/components/ui/Modal.svelte';
+	import EmptyState from '$lib/components/ui/EmptyState.svelte';
+	import PlaylistForm from '$lib/components/ui/PlaylistForm.svelte';
+	import Button from '$lib/components/ui/Button.svelte';
+
+	const playlistNames = [
+		'Mi Playlist',
+		'Tus favoritos',
+		'Lo mejor de hoy',
+		'Para relajarse',
+		'Buena vibra',
+		'Modo estudio',
+		'Road Trip',
+		'Domingos',
+		'Late Night',
+		'Descubriendo música',
+		'Todo un poco',
+		'En bucle',
+		'Mi colección',
+		'Canciones para repetir',
+		'Hits del momento'
+	];
+	const namePlaceholder = playlistNames[Math.floor(Math.random() * playlistNames.length)];
+
+	let { data, form } = $props();
+
+	const items = $derived(data.playlists.items);
+	const trackIds = $derived(data.trackIds);
+
+	let creating = $state(false);
+
+	function openCreate() {
+		creating = true;
+	}
+</script>
+
+<svelte:head>
+	<title>Mis listas · Musify</title>
+	<meta name="description" content="Mis listas en Musify." />
+</svelte:head>
+
+<Page>
+	<PageHeader title="Mis listas" subtitle="Crea y organiza tus colecciones.">
+		{#snippet actions()}
+			{#if items.length > 0}
+				<Button onclick={openCreate}>
+					<Plus class="h-4 w-4" strokeWidth={2.5} />
+					Crear lista
+				</Button>
+			{/if}
+		{/snippet}
+	</PageHeader>
+
+	{#if items.length > 0}
+		<MediaGrid class="mt-9">
+			{#each items as playlist, i (playlist.id)}
+				<PlaylistCard
+					id={playlist.id}
+					name={playlist.name}
+					description={playlist.description}
+					trackIds={trackIds[playlist.id] ?? []}
+					updatedAt={playlist.updatedAt}
+					index={i}
+				/>
+			{/each}
+		</MediaGrid>
+	{:else}
+		<EmptyState
+			icon={ListMusic}
+			title="Todavía no tienes listas"
+			description="Crea la primera y añádele canciones de tu biblioteca."
+		>
+			{#snippet actions()}
+				<Button onclick={openCreate}>
+					<Plus class="h-4 w-4" strokeWidth={2} />
+					Crear lista
+				</Button>
+			{/snippet}
+		</EmptyState>
+	{/if}
+</Page>
+
+<Modal open={creating} onClose={() => (creating = false)} title="Nueva lista">
+	<PlaylistForm
+		action="?/create"
+		{namePlaceholder}
+		formMessage={form?.message}
+		submitLabel="Crear"
+		submittingLabel="Creando…"
+		onCancel={() => (creating = false)}
+	/>
+</Modal>