Underline "built by OSU NLP Group" byline to cue the link

Reason: byline is a link to x.com/osunlp but looked like plain text;
add a subtle muted underline that shifts to the terracotta accent on
hover so users can see it's clickable.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app.py

@@ -311,11 +311,17 @@ gradio-app > div {
   color: var(--q-muted);
   font-size: 0.9rem;
   font-weight: 500;
-  text-decoration: none;
+  text-decoration: underline;
+  text-decoration-color: rgba(100,116,139,0.45);
+  text-underline-offset: 3px;
+  text-decoration-thickness: 1px;
   width: fit-content;
-  transition: color 140ms ease;
+  transition: color 140ms ease, text-decoration-color 140ms ease;
+}
+.quest-header-byline:hover {
+  color: var(--q-accent);
+  text-decoration-color: var(--q-accent);
 }
-.quest-header-byline:hover { color: var(--q-accent); }
 
 /* === Cards (section-card) =============================================== */
 .section-card {