Add top margin to homepage stat card; minor whitespace cleanup

- components/_cards.scss: .stat-card gets margin-top: 2rem; rebuilt
  styles.css to match.
- index.php: strip trailing whitespace on a blank line in the music
  section.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/scss/components/_cards.scss

@@ -9,6 +9,7 @@
 }
 
 .stat-card {
+  margin-top: 2rem;
   padding: 2rem;
   border-radius: 0.2rem;
 }

styles.css

@@ -293,6 +293,7 @@ section {
 }
 
 .stat-card {
+  margin-top: 2rem;
   padding: 2rem;
   border-radius: 0.2rem;
 }