The exact-path rule for /api/v1/setup matched only the bare path, so
sub-paths like /api/v1/setup/sessions fell through to the generic
/api/v1/{svc}/* rule and the gateway tried to dispatch to a synthetic
"setup" microservice. Swap the exact route for a prefix-aware route
that sends /api/v1/setup* to platform, add integration/smoke coverage,
and refresh the local frontdoor config accordingly.
Closes BOOTSTRAP-001 from SPRINT_20260413_004.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>