feat(3d-abacus): change default columns from 13 to 4

4 columns is a more practical default for initial preview and printing.
13 columns produces very large files and takes longer to render.

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

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

apps/web/src/app/create/abacus/page.tsx

@@ -7,7 +7,7 @@ import { css } from '../../../../styled-system/css'
 
 export default function ThreeDPrintPage() {
   // New unified parameter system
-  const [columns, setColumns] = useState(13)
+  const [columns, setColumns] = useState(4)
   const [scaleFactor, setScaleFactor] = useState(1.5)
   const [widthMm, setWidthMm] = useState<number | undefined>(undefined)
   const [format, setFormat] = useState<'stl' | '3mf' | 'scad'>('stl')