fix: update spaces-auth e2e assertion for ats:// scheme
Florian's #20 (469bf65) renamed the space URI scheme from at:// to ats://
across the codebase but didn't update the regex in this assertion (added
in PR #18 after that rename was already in flight).
Verified: pnpm test:e2e in apps/contrail-e2e — 12/12 passing.