Verify the deploy actually came up, not just that it was launched

systemctl restart (Type=simple, no readiness protocol) returns as
soon as podman compose up --build forks, before the build or the
container start have actually finished - a build failure or crash
loop would still show as a green deploy job. Poll /api/health for up
to 5 minutes (comfortably above the ~3.5min worst-case cold rebuild)
and fail the job if it never answers.

docs/deployment.adoc

@@ -246,3 +246,8 @@ a retagged image's old layers behind — turning every deploy into a
 full `apt-get`/`bundle install` from scratch (~3 minutes measured,
 vs. ~20s before). Fixed by adding `--build` to the unit instead (see
 above); don't reintroduce the `podman rmi` step.
+. Polls `http://localhost:4567/api/health` (up to 5 minutes, the job
+  fails if it never comes up) before calling the deploy done — the
+  restart above only confirms `podman compose up --build` was
+  launched (`Type=simple` has no readiness protocol), not that the
+  build actually succeeded and Puma is answering.