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/CoverBadge.svelte

@@ -0,0 +1,14 @@
+<script lang="ts">
+	interface Props {
+		label: string;
+		class?: string;
+	}
+
+	let { label, class: klass = '' }: Props = $props();
+</script>
+
+<span
+	class="pointer-events-none absolute top-2 left-2 rounded-full bg-black/45 px-2 py-0.5 text-[10px] font-semibold tracking-[0.08em] text-white uppercase backdrop-blur-sm {klass}"
+>
+	{label}
+</span>