clean TUI core

- Stripped forced-scrollbar hack from _menu and _checklist
- Eliminated TUI_ANCHO_REFORZADO overflow across 9 files
- Removed redundant _inst() function globally
- Added dynamic list height calculation for checklists
- Introduced Desktop & Display menu (Option 12)
- Fixed non-free-firmware false positive in repo detection
- Restored terminal transparency for apt/vainfo output"

modules/desktop_display.sh

@@ -0,0 +1,73 @@
+#!/usr/bin/env bash
+
+manage_desktop_display() {
+    while true; do
+        local choice
+        choice=$(_menu "Desktop & Display" \
+            "Select an option:" $TUI_ALTO $TUI_ANCHO 6 \
+            "1" "Desktop Environment" \
+            "2" "Display Manager" \
+            "3" "Back to main menu")
+        [ -z "$choice" ] && break
+        clear
+        case "$choice" in
+            1) _msg "Coming Soon" "Desktop Environment management will be available in a future update." 10 60 ;;
+            2) display_manager_menu ;;
+            3) break ;;
+        esac
+    done
+}
+
+display_manager_menu() {
+    while true; do
+        local choice
+        choice=$(_menu "Display Manager" \
+            "Select an option:" $TUI_ALTO $TUI_ANCHO 6 \
+            "1" "LightDM" \
+            "2" "Back")
+        [ -z "$choice" ] && break
+        clear
+        case "$choice" in
+            1) lightdm_config_menu ;;
+            2) break ;;
+        esac
+    done
+}
+
+lightdm_config_menu() {
+    local -a items=()
+    items+=("install_lightdm"   "Install LightDM & GTK Greeter" "$(_state lightdm)")
+    items+=("enable_userlist"   "Enable user list"             "OFF")
+    local choices
+    choices=$(_checklist "LightDM Configuration" \
+        "Select options to apply:" $TUI_ALTO $TUI_ANCHO $TUI_ALTO_LISTA \
+        "${items[@]}")
+    if [ -z "$choices" ]; then
+        echo "No changes."
+        _pause
+        return
+    fi
+    local cleaned
+    cleaned=$(echo "$choices" | tr -d '"')
+    for item in $cleaned; do
+        case $item in
+            install_lightdm)
+                if is_installed lightdm; then
+                    echo -e "${GREEN}LightDM is already installed.${NC}"
+                else
+                    _run_cmd "LightDM" "sudo apt install -y lightdm lightdm-gtk-greeter-settings" "Installing LightDM..."
+                fi
+                ;;
+            enable_userlist)
+                local conf="/etc/lightdm/lightdm.conf.d/50-debianito-userlist.conf"
+                if echo "[Seat:*]
+greeter-hide-users=false" | sudo tee "$conf" > /dev/null; then
+                    echo -e "${GREEN}User list enabled in LightDM.${NC}"
+                else
+                    echo -e "${RED}Failed to write configuration.${NC}"
+                fi
+                ;;
+        esac
+    done
+    _pause
+}