Fix navbar layout, card spacing, and background hierarchy

- Restore centered DiscDrop branding in navbar
- Navbar bg: base-300 (darkest)
- Cards bg: base-200 (intermediate), hover: base-300 (matches navbar)
- Body bg: base-100 (lightest)
- Card gap increased from gap-4 to gap-6

src/main/resources/templates/fragments/search-results.html

@@ -1,4 +1,4 @@
-<div class="bg-base-100 shadow-xl border border-base-300 rounded-box mt-1" style="max-height:24rem;overflow-y:auto">
+<div class="bg-base-200 shadow-xl border border-base-300 rounded-box mt-1" style="max-height:24rem;overflow-y:auto">
   {#if artists.isEmpty()}
     <div class="p-6 text-sm text-center" style="color:var(--bc);opacity:0.5">No artists found</div>
   {#else}