Update to latest Tufte CSS with dark mode support

- Updated to latest version from tufte-css repository
- Kept existing font paths (/static/fonts/)
- Adds dark mode support via prefers-color-scheme
- Minor improvements and updates from upstream

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

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

kjvstudy_org/static/tufte.css

@@ -52,6 +52,14 @@ body {
     counter-reset: sidenote-counter;
 }
 
+/* Adds dark mode */
+@media (prefers-color-scheme: dark) {
+    body {
+        background-color: #151515;
+        color: #ddd;
+    }
+}
+
 h1 {
     font-weight: 400;
     margin-top: 4rem;