fedora-intune: fix boot issues, add Himmelblau variant

Fixes found by building and inspecting the image:

- Select the Intune authselect profile with-altfiles. Without it system
  users in /usr/lib/passwd (gdm, pipewire, mdatp) do not resolve and the
  login screen never starts. The build now fails if gdm does not resolve.
- Ship /opt as a plain directory (opt-usrlocal: root). Defender installs
  to /opt/microsoft/mdatp and keeps state in /var/opt/microsoft/mdatp;
  with the default /opt -> /var/opt symlink those were the same
  read-only directory. rpm-ostree still relocates /opt content to
  /usr/lib/opt, so finalize.d/60-opt-links links it back (only for images
  where /opt is a directory; fedora-cosmic/remote are unaffected).
- Run Defender's %post on first boot (mdatp-firstboot.service): in a
  compose /var is read-only and the machine GUID/state must not be
  shared. mdatp.service waits for it.

New image fedora-intune-himmelblau: the same workstation with Entra ID
sign-in through Himmelblau (Community Nightly packages), which joins the
device at the first sign-in and enrolls it in Intune (apply_policy)
instead of the Microsoft Intune app. Workstation, Edge and Defender
manifests move to images/shared so both images use them; build.sh copies
images/shared/*.yaml and CI builds both images in one matrix job.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

images/shared/files/10-workstation-sshd.conf

@@ -0,0 +1,6 @@
+# Key-only SSH for local accounts (add keys to ~/.ssh/authorized_keys).
+PubkeyAuthentication yes
+PermitRootLogin no
+PasswordAuthentication no
+PermitEmptyPasswords no
+KbdInteractiveAuthentication no

images/shared/files/50-defender.preset

@@ -0,0 +1,4 @@
+# Defender: first-boot setup, the daemon and its network filter.
+enable mdatp-firstboot.service
+enable mdatp.service
+enable mde_netfilter_v2.socket

images/shared/files/50-workstation.preset

@@ -0,0 +1,3 @@
+enable gdm.service
+enable qemu-guest-agent.service
+enable sshd.service

images/shared/files/finalize.d/60-opt-links

@@ -0,0 +1,20 @@
+#!/bin/bash
+# Runs in the target root during `rpm-ostree compose image` (edition 2024
+# finalize.d hook). rpm-ostree relocates RPM content under /opt to
+# /usr/lib/opt. With `opt-usrlocal: root` /opt is a plain directory in the
+# image and nothing links it back, so link each vendor directory. Images on the
+# default (/opt -> /var/opt, linked by tmpfiles.d) are left alone.
+set -euo pipefail
+
+root="${PWD}"
+
+[[ -d "${root}/usr/lib/opt" ]] || exit 0
+if [[ -L "${root}/opt" || ! -d "${root}/opt" ]]; then
+  exit 0
+fi
+
+for dir in "${root}"/usr/lib/opt/*; do
+  name="$(basename "${dir}")"
+  ln -sfn "../usr/lib/opt/${name}" "${root}/opt/${name}"
+  echo "Linked /opt/${name} -> /usr/lib/opt/${name}"
+done

images/shared/files/mdatp-firstboot

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Finish the Defender (mdatp) install on first boot by running the package's
+# own %post, saved at build time: it creates the machine GUID, state, logs and
+# definitions database under /var and then enables and starts mdatp.service.
+set -euo pipefail
+
+MARKER=/var/lib/mdatp-firstboot.done
+
+[[ -f "${MARKER}" ]] && exit 0
+
+# mdatp.service only starts once the marker exists (10-firstboot.conf), and the
+# %post starts it, so create the marker first and drop it again on failure.
+touch "${MARKER}"
+if ! bash /usr/libexec/mdatp-postinst 1; then
+  rm -f "${MARKER}"
+  exit 1
+fi

images/shared/files/mdatp-firstboot.conf

@@ -0,0 +1,3 @@
+# Don't start Defender before mdatp-firstboot.service has created its state.
+[Unit]
+ConditionPathExists=/var/lib/mdatp-firstboot.done

images/shared/files/mdatp-firstboot.service

@@ -0,0 +1,15 @@
+[Unit]
+Description=Finish the Microsoft Defender for Endpoint install on first boot
+Documentation=https://learn.microsoft.com/en-us/defender-endpoint/microsoft-defender-endpoint-linux
+After=network-online.target
+Wants=network-online.target
+ConditionPathExists=!/var/lib/mdatp-firstboot.done
+
+[Service]
+Type=oneshot
+ExecStart=/usr/libexec/mdatp-firstboot
+RemainAfterExit=yes
+TimeoutStartSec=15min
+
+[Install]
+WantedBy=multi-user.target