Config in TOML and a metrics page

#Breaking

• relay.toml is the new config format. JavaScript config allowed arbitrary code at parse time, which made deploys slower and config un-diffable. relay migrate-config converts existing projects in place; relay.config.js still loads with a warning until 1.0.

#Added

• Metrics page. p50/p95/p99 latency, request volume, and error rate per route over the last 7 days. No setup, it is on for every project.
• relay secrets pull writes a local .env.relay for development, and relay secrets diff shows drift between local and deployed values.

#Improved

• Deploy output now groups changes by route and shows a diff summary instead of a wall of filenames.