System-Wide Refactor & Critical Fixes

- Resolved NVIDIA driver management issues by expanding package detection patterns (including nvidia-open and nvidia-kernel-open-dkms), enhancing purge process to ensure clean uninstallation of v590/595 drivers, and adding conditional skip for manage menu when no driver is installed.  
- Enhanced Firefox variant selection in internet.sh using exact token matching (grep -qx) instead of substring search to prevent incorrect removal or unintended ESR/Firefox conflicts. 
- New XFCE install option with 4 options
- Restructured Desktop Environment into two-level menu system with dispatcher and Xfce sub-menu for scalability, enabling future additions like GNOME/KDE without disrupting existing flows.  
- Added Polkit rules in desktop_display.sh to grant suspend permissions without password prompts on laptops, including idempotent group (backlight) creation and user membership management with || true fallbacks.  
- Enforced LC_ALL=C LANGUAGE=C environment variables for all dpkg-reconfigure commands across System Preferences and utils.sh to ensure native dialogues run consistently in English.  
- Fixed kernel backports menu option availability to only appear on Debian 13, preventing errors on Debian 12 where backports repositories are EOL.  
- Improved ZRAM module initialization sequence by ensuring swapoff and zram module removal occur before writing new configuration files to prevent race conditions during system setup.

modules/system/system_prefs.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+# system_prefs.sh — System Preferences: time, locale, keyboard, audio
+
+_prefs_date_time() {
+    echo -e "${YELLOW}Current system date/time:${NC} $(date '+%Y-%m-%d %H:%M')"
+    echo -e "${YELLOW}Timezone:${NC} $(timedatectl show -p Timezone --value 2>/dev/null || echo unknown)"
+
+    if _confirm "Timezone" "Change the system timezone (dpkg-reconfigure tzdata)?"; then
+        sudo env LC_ALL=C LANGUAGE=C dpkg-reconfigure tzdata || true
+        echo -e "${GREEN}Timezone: $(timedatectl show -p Timezone --value 2>/dev/null)${NC}"
+    fi
+    _ensure_time_synced
+}
+
+_prefs_locale_keyboard() {
+    sudo env LC_ALL=C LANGUAGE=C dpkg-reconfigure locales || true
+    sudo env LC_ALL=C LANGUAGE=C dpkg-reconfigure keyboard-configuration || true
+    echo -e "${GREEN}Language, locales and keyboard configured.${NC}"
+}
+
+_prefs_audio() { _prefs_audio_menu; }
+
+_system_preferences_menu() {
+    while true; do
+        local choice
+        choice=$(_menu "System Preferences" "Select a preference group:" \
+            $TUI_ALTO $TUI_ANCHO $TUI_ALTO_LISTA \
+            "1" "Date, Time & Timezone" \
+            "2" "Language, Locales & Keyboard" \
+            "3" "Audio & Sound Stack" \
+            "4" "Back to main menu")
+        [ -z "$choice" ] && return
+        clear
+        case "$choice" in
+            1) _prefs_date_time ;;
+            2) _prefs_locale_keyboard ;;
+            3) _prefs_audio ;;
+            4) return ;;
+        esac
+    done
+}