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/os-release

@@ -0,0 +1,11 @@
+NAME="Antergos NeXT"
+PRETTY_NAME="Antergos NeXT"
+ID=antergos
+ID_LIKE=artix
+BUILD_ID=rolling
+ANSI_COLOR="38;2;0;136;204"
+HOME_URL="https://github.com/Antergos-NeXT"
+DOCUMENTATION_URL="https://wiki.archlinux.org"
+SUPPORT_URL="https://github.com/Antergos-NeXT"
+BUG_REPORT_URL="https://github.com/Antergos-NeXT"
+LOGO=antergos-logo