feat(studio): support user pool runtime authentication

[evanlowe]

Summary

• add API Key (default) and Identity user-pool authentication to the Studio Runtime deployment page
• list Identity user pools through the Studio backend, mark the current Studio pool, and preserve authentication on Runtime updates
• forward validated Studio JWTs through the Runtime proxy for JWT-authenticated Runtimes
• add backend and frontend coverage, documentation, and rebuilt Studio assets

Testing

• pre-commit run --all-files
• pytest — 1113 passed, 5 skipped
• npm test — 365 passed
• npm run build
• live end-to-end check with a temporary user-pool-authenticated Runtime: authenticated /run_sse succeeded, while unauthenticated proxy and direct Runtime requests returned 401; temporary resources were removed