Add alvin-install TUI installer, fix NetworkManager boot

- New gum-based installer script (alvin-install) with LUKS encryption,
  nmtui networking, disk selector, user/git config, and CachyOS repo setup
- Replace NetworkManager full unit file with symlink for consistency
- Add alvin-install reference to MOTD
- Add file_permissions entry in profiledef.sh
- Fix localrepo path case in pacman.conf

profiledef.sh

@@ -20,6 +20,7 @@ file_permissions=(
   ["/root/.automated_script.sh"]="0:0:755"
   ["/root/.gnupg"]="0:0:700"
   ["/usr/local/bin/choose-mirror"]="0:0:755"
+  ["/usr/local/bin/alvin-install"]="0:0:755"
   ["/usr/local/bin/Installation_guide"]="0:0:755"
   ["/usr/local/bin/livecd-sound"]="0:0:755"
 )