Increase tutorial header title font size

Increased the font size from 1rem to 1.25rem to make the tutorial title more prominent in the header while maintaining visual balance with the description text.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: strickvl

assets/main.css

@@ -319,7 +319,7 @@ header {
 }
 
 .tutorial-title h2 {
-  font-size: 1rem;
+  font-size: 1.25rem;
   font-weight: 600;
   color: var(--zenml-dark);
   margin: 0;