Release v1.2.0: Template-based deployment with custom domains

- Add wrangler.toml.template files with placeholders for sensitive data
- Create comprehensive deploy.js with 8-step deployment pipeline
- Create dev.js for local development with auto port management
- Add bump-version.js for version management across all packages
- Move .env to project root for centralized secrets
- Add custom domain support via {{ADMIN_DOMAIN}} and {{WEBHOOK_DOMAIN}} placeholders
- Update Rust worker crate to 0.7.2
- Remove legacy scripts (deploy-fullstack, dev-fullstack, setup-database, setup-kv, upload-secrets)