refactor: name an artist mix after the artist alone

The "Mezcla:" prefix repeated what the header label already says, and it
pushed the long titles into an extra line on the detail page.

backend/Musify.Application/Mixes/GenerateMixesForUser.cs

@@ -256,7 +256,7 @@ namespace Musify.Application.Mixes
                     continue;
 
                 drafts.Add(new MixDraft(
-                    Truncate($"Mezcla: {seed.Name}", MixTitleLength),
+                    Truncate(seed.Name, MixTitleLength),
                     $"Canciones de {seed.Name} y de artistas parecidos.",
                     items));
             }

web-player/src/routes/(app)/mixes/[id]/+page.svelte

@@ -83,7 +83,7 @@
 			class="h-36 w-36 shrink-0 rounded-art-lg shadow-art-lg sm:h-44 sm:w-44"
 		/>
 		<div class="min-w-0 flex-1">
-			<p class="text-sm tracking-[0.14em] text-fg-3 uppercase">Mix</p>
+			<p class="text-sm tracking-[0.14em] text-fg-3 uppercase">Mezcla</p>
 			<h1
 				class="mt-1.5 text-3xl font-bold tracking-tight break-words text-fg sm:text-5xl md:text-7xl"
 			>