Deploy: Add Cloudflare Worker, D1 database integration, and updated README

- Add complete Cloudflare Worker implementation with waitlist API endpoints
- Integrate Cloudflare D1 SQLite database for production waitlist storage
- Add wrangler configuration for Worker deployment and D1 binding
- Rewrite README with comprehensive deployment and architecture documentation
- Update environment configuration and build setup
- Add waitlist utility functions and API client
- Update project dependencies and Vite configuration
- Deploy live to https://react-example.white-glade-ab2c.workers.dev

wrangler.jsonc

@@ -0,0 +1,11 @@
+{
+  "$schema": "node_modules/wrangler/config-schema.json",
+  "name": "react-example",
+  "compatibility_date": "2026-08-28",
+  "observability": {
+    "enabled": true
+  },
+  "assets": {
+    "not_found_handling": "single-page-application"
+  }
+}