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/root-overlay/etc/pacman.conf

@@ -0,0 +1,31 @@
+#
+# /etc/pacman.conf
+#
+# See the pacman.conf(5) manpage for option and repository directives
+
+#
+# GENERAL OPTIONS
+#
+[options]
+HoldPkg     = pacman glibc
+Architecture = auto
+CheckSpace
+ParallelDownloads = 5
+DownloadUser = alpm
+
+SigLevel    = Required DatabaseOptional
+LocalFileSigLevel = Optional
+
+# Antergos NeXT custom packages repo
+[antergos-pkgs]
+SigLevel = Optional TrustAll
+Server = https://antergos-next.github.io/antergos-packages/
+
+[system]
+Include = /etc/pacman.d/mirrorlist
+
+[world]
+Include = /etc/pacman.d/mirrorlist
+
+[galaxy]
+Include = /etc/pacman.d/mirrorlist