feat: add Antergos NeXT Minimal (Xfce) profile — lightweight ISO edition

Introduces iso-profiles/antergos-minimal/, a new Xfce-based profile for
building a lightweight Antergos NeXT ISO under the 2 GB GitHub Releases
limit (the full Plasma profile produces ~2.15 GB).

Profile structure:
- profile.yaml: Xfce4 desktop, dinit-only init packages, Falkon browser,
  minimal app selection, antergos-xfce-theme included in rootfs
- root-overlay/: SDDM configured for xfce.desktop, GRUB theme pointed to
  antergos, xfconf settings for Antergos-NeXT GTK/xfwm4 theme
- live-overlay/: Calamares offline + online configs, netinstall with
  multiple DE options (Plasma, Xfce, Cinnamon, MATE, LXQt, i3, Sway,
  Hyprland), notesqml@minimal-info step explaining the edition rationale,
  basestrap operations for antergos-release/grub-theme/keyring, display
  manager selection (SDDM/LightDM/LXDM/LY), audio services (pipewire),
  and antergos-xfce-theme in the Xfce subgroup

Default Xfce theme is set to Antergos-NeXT (Numix-derived, blue accent)
via xfconf XML in both live-overlay and root-overlay skel directories.

iso-profiles/antergos-minimal/live-overlay/etc/calamares-offline/modules/users.conf

@@ -0,0 +1,49 @@
+---
+defaultGroups:
+    - name: users
+      must_exist: true
+      system: true
+    - lp
+    - video
+    - network
+    - storage
+    - name: wheel
+      must_exist: false
+      system: true
+    - audio
+    - power
+    - log
+    - optical
+    - network
+    - scanner
+
+autologinGroup: autologin
+
+doAutologin:     false
+
+sudoersGroup:    wheel
+
+setRootPassword: true
+
+doReusePassword: false
+
+passwordRequirements:
+    nonempty: true
+    minLength: 4  # Password at least this many characters
+    maxLength: -1  # Password at most this many characters
+    libpwquality:
+        - minlen=4
+        - minclass=0
+
+allowWeakPasswords: true
+allowWeakPasswordsDefault: true
+
+userShell: /bin/bash
+
+setHostname: EtcFile
+
+writeHostsFile: true
+
+user:
+  shell: /bin/bash
+  forbidden_names: [ root ]