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/default/grub

@@ -0,0 +1,53 @@
+GRUB_DEFAULT="0"
+GRUB_TIMEOUT="3"
+GRUB_DISTRIBUTOR="Antergos NeXT"
+GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
+GRUB_CMDLINE_LINUX="net.ifnames=0"
+
+# Preload both GPT and MBR modules so that they are not missed
+GRUB_PRELOAD_MODULES="part_gpt part_msdos"
+
+# Uncomment to enable Hidden Menu, and optionally hide the timeout count
+#GRUB_HIDDEN_TIMEOUT="5"
+#GRUB_HIDDEN_TIMEOUT_QUIET="true"
+
+# Uncomment to use basic console
+GRUB_TERMINAL_INPUT="console"
+
+# Uncomment to disable graphical terminal
+#GRUB_TERMINAL_OUTPUT="console"
+
+# The resolution used on graphical terminal
+# note that you can use only modes which your graphic card supports via VBE
+# you can see them in real GRUB with the command `vbeinfo'
+#GRUB_GFXMODE="1680x1050x8"
+GRUB_GFXMODE="1024x768,800x600"
+
+# Uncomment to allow the kernel use the same resolution used by grub
+GRUB_GFXPAYLOAD_LINUX="keep"
+
+# Uncomment if you want GRUB to pass to the Linux kernel the old parameter 
+# format "root=/dev/xxx" instead of "root=/dev/disk/by-uuid/xxx" 
+#GRUB_DISABLE_LINUX_UUID="true"
+
+# Uncomment to disable generation of recovery mode menu entries
+GRUB_DISABLE_RECOVERY="true"
+
+# Uncomment and set to the desired menu colors.  Used by normal and wallpaper 
+# modes only.  Entries specified as foreground/background.
+export GRUB_COLOR_NORMAL="light-blue/black"
+export GRUB_COLOR_HIGHLIGHT="light-cyan/blue"
+
+# Uncomment one of them for the gfx desired, a image background or a gfxtheme
+#GRUB_BACKGROUND="/path/to/wallpaper"
+GRUB_THEME="/usr/share/grub/themes/antergos/theme.txt"
+
+# Uncomment to get a beep at GRUB start
+#GRUB_INIT_TUNE="480 440 1"
+
+GRUB_SAVEDEFAULT="true"
+
+GRUB_DISABLE_LINUX_RECOVERY="true"
+
+# Probe for other installed operating systems
+GRUB_DISABLE_OS_PROBER="false"