BUY-5602: Commit portal CI/CD workflows to repo

[BuyWhere]

Summary

• Adds 15 CI/CD workflow files to .github/workflows/
• Workflows sourced from bolt/add-staging-build-job-v5 branch which has the latest production-ready configurations

Workflows added

• deploy-cloud-run-production.yml - Production Cloud Run deployment
• deploy-cloud-run-staging.yml - Staging Cloud Run deployment
• deploy-frontend-vercel.yml - Vercel frontend deployment
• deploy-logging-production.yml - Production logging setup
• deploy-mcp-cloud-run-production.yml - MCP Cloud Run production
• deploy-static-site.yml - Static site deployment
• deploy-us.yml - US region deployment
• docs.yml - GitHub Pages documentation
• enable-pg-stat-statements-staging.yml - PG stats staging
• inject-posthog-vm.yml - PostHog VM injection
• nginx-deploy.yml - Nginx config deployment
• publish-python-sdk.yml - Python SDK publishing
• sentry-alerts.yml - Sentry alerting
• ssl-renewal.yml - SSL certificate renewal
• update-cloud-run-sentry.yml - Cloud Run Sentry update

Next steps

• Review and merge to master
• Workflows will then be active for CI/CD operations