Increase server API rate limits by 5x

[noodleonthecape]

Summary

• increase server API request rate limits by 5x for free, pro, and enterprise plans
• keep middleware plan-level rate_per_min constants aligned with runtime rate limiting
• update rate limit middleware tests to match the new thresholds and route multiplier behavior

Validation

• npm test --workspace @relaycast/server
• npm run build --workspace @relaycast/server

[github-actions]

Preview deployed!

Environment	URL
API	https://pr108-api.relaycast.dev
Health	https://pr108-api.relaycast.dev/health
Observer	https://pr108-observer.relaycast.dev/observer

This preview shares the staging database and will be cleaned up when the PR is merged or closed.

Run E2E tests

npm run e2e -- https://pr108-api.relaycast.dev --ci

Open observer dashboard

https://pr108-observer.relaycast.dev/observer

[noodleonthecape]

Closing this since the rate-limit changes were folded into #107.