Match _public_presentations hero gradient styling

.course-hero now uses the same blue→purple gradient panel, larger
border-radius/padding, and Outfit-800 h1 as .site-hero in the
public_presentations site. Syllabus content is unchanged.

Author: PhilippPelz

index.qmd

@@ -52,13 +52,14 @@ execute:
 ```{=html}
 <style>
 .course-hero {
-  background: rgba(20, 25, 40, 0.65);
-  border: 1px solid rgba(255,255,255,0.06);
-  border-radius: 18px;
-  padding: 1.5rem;
-  margin: 1rem 0 2rem 0;
-  backdrop-filter: blur(10px);
+  background: linear-gradient(135deg, rgba(59,130,246,0.18), rgba(139,92,246,0.14));
+  border: 1px solid rgba(255,255,255,0.08);
+  border-radius: 24px;
+  padding: 2.5rem 3rem;
+  margin: 2rem 0 3rem 0;
+  text-align: left;
 }
+.course-hero h1 { font-family: "Outfit", sans-serif; font-weight: 800; margin-bottom: 0.5rem; border: none; }
 .course-kicker {
   text-transform: uppercase;
   letter-spacing: 0.08em;
@@ -101,6 +102,7 @@ execute:
   margin: 1.25rem 0 2rem 0;
 }
 @media (max-width: 768px) {
+  .course-hero { padding: 2rem; }
   .course-meta-grid { grid-template-columns: 1fr; }
 }
 </style>