* feat(gateway): add /startupz startup probe with auth-gated version detail
Startup/traffic-admission probe that excludes downstream channel health:
200 started once startup work completes and the gateway is not draining,
503 starting/draining otherwise. Version and uptime are only included for
local-direct or authenticated callers, reusing the /readyz detail gate.
* fix(deploy): use /startupz for traffic admission in bundled templates
fly.toml gains its missing HTTP check; render.yaml stops using pure
liveness as admission; k8s pins an immutable image tag, seeds config
only when missing, and adds a startupProbe; stale Fly healthcheck-port
doc corrected (healthcheck follows the active gateway lock port since
bc4221a07e).
* docs(k8s): make persistent-file config ownership explicit with reseed path
Peter Steinberger