fedora-remote: minimal headless GNOME Remote Desktop host with Kanidm

New image built from upstream base-atomic (no desktop), adding only gnome-shell
+ gdm + gnome-remote-desktop + pipewire/portal + foot + Flatpak + Kanidm.
recommends=false to stay lean. Configures GNOME Remote Desktop headless remote
login on first boot (TLS + credentials + enable). Firefox preinstalled as a
per-user Flatpak. Add it to the CI matrix and prune both images.

images/fedora-remote/repos/44/network-idm.repo

@@ -0,0 +1,9 @@
+[network_idm]
+name=Identity Management related tools (Fedora 44)
+baseurl=https://download.opensuse.org/repositories/network:/idm/Fedora_44/
+type=rpm-md
+skip_if_unavailable=False
+gpgcheck=1
+repo_gpgcheck=0
+enabled=1
+gpgkey=https://download.opensuse.org/repositories/network:/idm/Fedora_44/repodata/repomd.xml.key