gdo in the vel's own stack, and portal v0.5.2

The mailer moves in. Portal decides what to send and publishes it on
this NATS; gdo is what hands it to a mail server, and it belongs here
rather than shared, so the vel's mail leaves on the vel's own terms. It
has no mail server of its own and relays through the host's - on kasse,
Klingenberg Bygg's postfix - which is the one thing this stack borrows
and the one line that changes if the vel ever gets a host of its own.

Also:

- portal v0.5.2, four releases on from the v0.3.36 this pinned.
- The Kanidm setup makes the onboarding service account and its token.
  The vel's desks invite neighbours, and portal needs a token to do it;
  without one every invite fails closed. It goes in
  idm_people_on_boarding, which may create a person and issue a first
  credential reset and nothing else, plus idm_people_pii_read so an
  invite finds someone who already has an account instead of making
  them a second one.
- The deploy workflow runs. It was pointed at a `tomtervel` runner
  label that has never existed, so every push queued and did nothing.
  It now runs on kasse's host runner, which is not root and may run one
  argumentless script that pulls this repo and brings the stack up.
- The hosts default to vel.klingenbergbygg.no and
  id.vel.klingenbergbygg.no, which is where this actually runs. Both
  already resolve to kasse.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

gdo/Dockerfile

@@ -0,0 +1,19 @@
+# gdo, the mailer, from the [uhhm] Arch registry - the same package the
+# bare-metal hosts install. Arch base rather than Debian because that is
+# how every uhhm binary is published; portal ships a release tarball and
+# is built from that instead.
+FROM archlinux:base
+ARG GDO_RELEASE
+RUN printf '%s\n' \
+      '[uhhm]' \
+      'SigLevel = Required DatabaseOptional' \
+      'Server = https://project.uhhm.no/api/packages/bl/arch/$repo/$arch' \
+    >> /etc/pacman.conf \
+ && pacman -Sy --noconfirm --needed ca-certificates gdo \
+ && pacman -Scc --noconfirm \
+ && rm -rf /var/cache/pacman/pkg/* /var/lib/pacman/sync/*
+# A non-root user; gdo writes nothing and holds no state - what it has
+# not yet delivered is on the stream, not on disk.
+RUN useradd --system --no-create-home gdo
+USER gdo
+CMD ["/usr/bin/gdo"]