Displays managers & zram menu

- LightDM Overhaul: Rewrote `install_lightdm()` logic to verify both lightdm and lightdm-gtk-gtk-greeter-settings. Now installs the trio in a single command if missing, skipping only when fully present. Added "Enable autologin" option modifying `/etc/lightdm/lightdm.conf` with robust `sed` patterns for `SUDO_USER`. Fixed missing `debconf-set-selections` to ensure LightDM is set as default during installation.
- GDM3 Implementation: Created a new sub-menu in `modules/desktop_display.sh` allowing independent installation of GDM3, User List toggle (hide/show), Autologin configuration via `/etc/gdm3/daemon.conf`, and conditional "Force Enable Wayland on NVIDIA" for Debian 12/13 using udev symlinks.
- SDDM Integration: Added SDDM as option 3 in the Display Manager menu. Implemented automatic session detection (Wayland > X11) to populate `/etc/sddm.conf.d/autologin.conf` without user input, defaulting to plasmawayland, lxqt-wayland, or generic fallbacks.
- greetd support: Added conditional support for Debian 12 and 13 only. Implemented sub-menu with base install, recommended `tuigreet` (with backports handling for Bookworm), and other manual setup options (`gtkgreet`, `nwg-hello`, `wlgreet`) exclusive to Trixie. 
- ZRAM UX Improvements: Updated descriptions in `modules/zram.sh` to explicitly mention I/O reduction and responsiveness benefits for low-RAM systems (e.g., 4GB). Cleaned up compression algorithm labels (`lz4`, `zstd`) to remove redundancy in menu values.
- General Code Quality: Standardized all user-facing messages to English across modules. Ensured independent package installation checks prevent script abortion if one DM fails, while maintaining strict error handling for system configurations.
- update docs and readme

modules/swap.sh

@@ -161,7 +161,7 @@ manage_swap() {
 
     while true; do
         local choice
-        choice=$(_menu "Swap Management (disk)" \
+        choice=$(_menu "Swap Management" \
             "Select an option:" $TUI_ALTO $TUI_ANCHO 6 \
             "1" "Show current swap & swappiness" \
             "2" "Create / resize swapfile" \