feat: add redirect from /board/* to canvas.jeffemmett.com

Old canvas board URLs now redirect to the new canvas subdomain:
- jeffemmett.com/board/mycofi -> canvas.jeffemmett.com/mycofi

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

next.config.mjs

@@ -7,6 +7,17 @@ const nextConfig = {
   images: {
     unoptimized: true,
   },
+  async redirects() {
+    return [
+      // Redirect old canvas board URLs to new canvas subdomain
+      // jeffemmett.com/board/mycofi -> canvas.jeffemmett.com/mycofi
+      {
+        source: '/board/:path*',
+        destination: 'https://canvas.jeffemmett.com/:path*',
+        permanent: true, // 308 redirect for SEO
+      },
+    ]
+  },
 }
 
 export default nextConfig