Remove duplicate h1, fix avatar gender caching, blacklist Celeste voice

- Hide h1 (sr-only) on homepage — banner already shows show name
- Promote tagline as visual lead after banner
- Fix avatar gender: add .gender marker files, re-fetch on mismatch
- Clear stale avatar cache so all re-fetch with correct gender
- Blacklist Celeste voice from caller pool

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

website/css/style.css

@@ -184,6 +184,13 @@ a:hover {
   line-height: 1.5;
 }
 
+.tagline--hero {
+  font-size: 1.4rem;
+  color: var(--text);
+  font-weight: 600;
+  max-width: 600px;
+}
+
 .phone {
   display: flex;
   align-items: center;