UI polish: centering, search width, dropdown contrast, cover thumbnails, branding, sticky headers

- Constrain main content to max-w-5xl centered
- Widen search input (w-72 md:w-80 lg:w-96)
- Search dropdown: card with shadow, border, and primary-tinted hover
- Branding: SVG music note icon + gradient text + tagline
- Covers: 64px with front-250 thumbnail URL for faster loading
- Badge colors per type (primary/secondary/accent/ghost)
- Sticky table headers via table-pin-rows
- SVG icons for Add/Remove/RSS/OPML buttons
- Consistent hover transitions across tables

src/main/resources/templates/artists.html

@@ -1,9 +1,9 @@
 {#include layouts/base}
 {#page-content}
-<div class="w-full max-w-4xl mx-auto">
-  <h2 class="text-2xl font-bold mb-4">🎤 Artists</h2>
+<div class="w-full">
+  <h2 class="text-2xl font-bold mb-5">🎤 Tracked Artists</h2>
   <div id="artist-list" hx-get="/api/artists/list" hx-trigger="load">
-    <span class="loading loading-spinner loading-lg block mx-auto"></span>
+    <span class="loading loading-spinner loading-lg block mx-auto my-12"></span>
   </div>
 </div>
 {/page-content}