Increase chapter number font size on book pages

Make chapter numbers more prominent and easier to click (1.8rem).

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

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

kjvstudy_org/templates/book.html

@@ -4,6 +4,11 @@
 
 {% block head %}
 <style>
+section h2 + p a {
+    font-size: 1.8rem;
+    font-weight: 500;
+}
+
 .popular-chapter {
     font-weight: bold;
 }