fix: configure Node.js 22 for Cloudflare Pages deployment

Cloudflare Pages was failing with Node.js 18.17.1, but Vite 7.1.9
requires Node.js 20.19+ or 22.12+.

Error from Cloudflare build:
  "You are using Node.js 18.17.1. Vite requires Node.js version 20.19+ or 22.12+"
  "[vite:build-html] crypto.hash is not a function"

Solution:
Added .node-version file to explicitly specify Node.js 22.
Cloudflare Pages will automatically detect and use this version.

This ensures consistency across all environments:
- Local: Node.js 24.1.0
- GitHub Actions CI: Node.js 22
- Cloudflare Pages: Node.js 22 (now configured)

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

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

Author: taearls

.node-version

@@ -0,0 +1 @@
+22