Complete archiso/Calamares profile scaffold (iso/)

- Calamares modules: unpackfs (clone), partition/mount/fstab (btrfs subvols),
  bootloader (systemd-boot + quiet splash), packages (strip live), services
  (greetd), shellprocess (snapper, flathub, strip-live), branding (Fuji)
- bootstrap-profile.sh: releng base + linux-zen swap + overlay our deltas
- BUILD.md: build steps, decisions, and honest open items (needs build-test)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

iso/overrides/airootfs/etc/calamares/modules/services-systemd.conf

@@ -0,0 +1,13 @@
+---
+services:
+- name: greetd            # the TANINUX login (tanin-greet) — its config is already
+  mandatory: false        #   in place from the tanin-greet package scriptlet
+- name: NetworkManager
+  mandatory: false
+- name: snapper-cleanup.timer
+  mandatory: false
+- name: snapper-timeline.timer
+  mandatory: false
+targets:
+- name: graphical
+  mandatory: true