Fix search, branding, header centering, and card-based feed layout

- Search box now fills navbar center with max-width 400px
- Dropdown items have more padding (p-4) and hover contrast
- Branding uses cross-browser gradient text with visible tagline
- Navbar centers tabs + search together in navbar-center
- Feed redesigned as responsive card grid (cover-centered, details below)
- Cards show large cover art with aspect-ratio:1, fallback SVG on 404
- Artist name, title, type badge, and date positioned under cover

src/main/resources/templates/releases.html

@@ -1,7 +1,7 @@
 {#include layouts/base}
 {#page-content}
 <div class="w-full">
-  <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.25rem">
+  <div style="display:flex;align-items:center;justify-content:space-between;margin-bottom:1.5rem;flex-wrap:wrap;gap:0.75rem">
     <h2 style="font-size:1.5rem;font-weight:700">📡 Releases</h2>
     <div style="display:flex;gap:0.5rem">
       <a href="/feed/rss.xml" class="btn btn-primary btn-sm gap-2">