fix: prevent horizontal overflow causing right-shifted layout

Animated blur blobs and absolute-positioned elements were overflowing
the viewport, creating a horizontal scrollbar that shifted all content.
Added overflow-x: hidden to html and body.

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

src/index.css

@@ -62,6 +62,9 @@
 }
 
 @layer base {
+  html, body {
+    overflow-x: hidden;
+  }
   body {
     @apply font-sans text-slate-800 bg-slate-50 antialiased;
   }