feat(web-player): rebuild Inicio and Buscar to the design handoff

Applies the handoff's layout and image shapes while keeping the current
Musify design system (Inter, colors, tokens) — no font or palette swap.

Inicio now stacks distinct shelves instead of repeated square grids:
recently played rows, a rail of recently listened albums with an "Álbum"
badge, a "Hecho para ti" bento of mixes, a rail of playlists with a
trailing dashed "Ver todas" tile, tall "Canciones nuevas" posters with a
"Nuevo" badge, a rail of circular top-artist avatars, and a recommended
rail. Buscar splits into Álbumes (square cards + badge), Usuarios (a
circular-avatar directory) and a flat Canciones list.

Top artists and the search user directory are filler data until the
backend exposes them. New shared pieces: Rail, CoverBadge, ArtistAvatar,
MixBentoTile. The orphaned TrackTile and MixCard are removed.

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

@@ -0,0 +1,23 @@
+<script lang="ts">
+	import type { Snippet } from 'svelte';
+
+	interface Props {
+		class?: string;
+		children: Snippet;
+	}
+
+	let { class: klass = '', children }: Props = $props();
+</script>
+
+<div class="no-scrollbar -mx-1 flex gap-4 overflow-x-auto px-1 pb-2 {klass}">
+	{@render children()}
+</div>
+
+<style>
+	.no-scrollbar {
+		scrollbar-width: none;
+	}
+	.no-scrollbar::-webkit-scrollbar {
+		display: none;
+	}
+</style>