Add Cloudflare Workers environment variables and update deployment documentation

Commit notes

- Introduced a new `.dev.vars` file for local development environment variables specific to Cloudflare Workers. - Updated `CLOUDFLARE_DEPLOY_STEPS.md` to reflect the addition of the new environment variables and clarified the deployment readiness status. - Created a new `tsconfig.cloudflare.json` for tailored TypeScript configuration for Cloudflare Workers. - Removed outdated React Router type definitions to streamline the codebase and improve maintainability.