Fix AutoInstaller GUI post-installation finalization

- Implement proper root password configuration matching auto-installer.sh:
  * Support preseed file passwords (both plain and crypted)
  * Copy live system root password hash when available
  * Set default password as fallback
  * Proper shadow file management and password aging

- Fix mbetterclient user creation with complete autologin setup:
  * Create user with proper home directory and bash shell
  * Remove password for autologin
  * Configure .bashrc for automatic X session launch on tty1
  * Create .xinitrc for proper X session with MBetterClient
  * Set proper file ownership

- Implement complete inittab configuration for autologin:
  * Configure getty for mbetterclient autologin on tty1
  * Maintain normal getty for other terminals
  * Proper runlevel configuration

- Add system cleanup functionality:
  * Remove live-specific systemd configurations
  * Remove live directories and profile configurations
  * Remove live initramfs hooks

- Enhance post-install cleanup:
  * Remove auto-installer script from installed system
  * Remove auto-installer log files
  * Run post-installation setup scripts if available

These changes ensure the installed system boots correctly with:
- Proper network configuration using selected interface
- Working root password (from live system or default)
- Automatic mbetterclient user login and MBetterClient startup
- Clean system without live-specific configurations