fix fresh install hang: split AGS into own module, remove obsolete packages

- Remove slow fallback loop from is_package_installed (only use expac)
- Move aylurs-gtk-shell from hyprland group to dedicated core/ags module
  with clear progress warning and user confirmation before build
- Install AUR packages one at a time in install_aur (better error isolation)
- Replace obsolete ttf-font-awesome with otf-font-awesome
- Remove p7zip (deleted from repos and AUR)

install.sh

@@ -19,6 +19,7 @@ export OMERON_FRESH_INSTALL
 DEFAULT_MODULES=(
   "core/preflight"
   "core/packages"
+  "core/ags"
   "core/dotfiles"
   "core/services"
   "homelab/setup"
@@ -29,6 +30,7 @@ DEFAULT_MODULES=(
 
 FRESH_MODULES=(
   "core/packages"
+  "core/ags"
   "core/dotfiles"
   "core/services"
   "homelab/setup"