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/fedora-intune-himmelblau/files/50-himmelblau-user.preset

@@ -0,0 +1,3 @@
+# Intune compliance check at login and on a timer, for every user.
+enable himmelblau-compliance-check.service
+enable himmelblau-compliance-check.timer

images/fedora-intune-himmelblau/files/50-himmelblau.preset

@@ -0,0 +1,4 @@
+# Himmelblau daemons; they pull in their sockets with Requires=.
+enable himmelblaud.service
+enable himmelblaud-tasks.service
+enable himmelblau-hsm-pin-init.service

images/fedora-intune-himmelblau/files/himmelblau.conf

@@ -0,0 +1,17 @@
+# Himmelblau configuration. See himmelblau.conf(5) and
+# https://himmelblau-idm.org/docs/reference/himmelblau-conf/
+#
+# No tenant settings are needed: `domain` defaults to the domain of the first
+# user who signs in, and that user joins the device to Entra ID. Restrict who
+# may sign in with pam_allow_groups (group object IDs or UPNs).
+
+[global]
+# Enroll the device in Intune and apply/report compliance policies.
+apply_policy = true
+# Fedora's admin group; members of sudo_groups (Entra group object IDs) are
+# added to it.
+local_sudo_group = wheel
+# Home directories named after the account (e.g. /home/jdoe), with a UPN alias.
+home_attr = CN
+home_alias = SPN
+use_etc_skel = true