Security hardening & DRY refactoring

- Fixed command injection in desktop_display.sh by converting word-splitting loops to safe array-based iteration for LightDM/GDM3 configuration and XFCE package installation.
- Added symlink detection guard before repository file operations in repos.sh to prevent TOCTOU attacks during restore_previous_repos().
- Hardened SUDO_USER resolution with awk validation against /etc/passwd to prevent root fallback and ensure real login users are targeted for sudoers configuration.
- Implemented algorithm (lz4/zstd) and size validation before ZRAM configuration writes in zram.sh to reject invalid inputs.
- Protected grep MemTotal read from /proc/meminfo with 2>/dev/null and default assignment under set -u.
- Added || true guards around apt-cache madison pipelines in firmware.sh, kernel.sh, gpu.sh, and utils.sh to prevent pipefail aborts when backports unavailable.
- Wrapped whiptail installation in if/else blocks to allow offline error messages instead of script termination under set -e.
- Fixed grep -c output duplication in swap.sh with proper || true pattern and default variable assignment.
- Replaced unquoted $cleaned loops with array conversion using while read for secure package iteration across gaming, desktop_display, firmware, and kernel modules.
- Anchored sed regex patterns to space-delimited "main" components to prevent mirror URL corruption in sources.list editing.
- Escaped % characters in _msg() function before passing to whiptail to prevent printf format interpretation crashes.
- Consolidated package version helpers into canonical wrappers: _get_pkg_version, _get_installed_version, _get_backports_version for consistent apt/dpkg queries.
- Created _install_if_missing() and _install_pkg() with proper error handling that respects set -e while providing user feedback on installation failures.
- Removed 6 dead code functions (~51 lines): check_system_time, sync_system_time, get_cpu_summary, get_ram_summary, pkg_versions, get_backports_kernel_version.
- Added detect_displayserver and detect_audio_server to refresh_system_state() for complete state refresh when returning from menus.
- Enhanced _on_interrupt() trap handler to kill lingering apt/dpkg child processes and clean /tmp/debianito.* temporary files on Ctrl+C or TERM.
- Improved restore_previous_repos() with manifest-based backup verification (.backed_up_* markers) to prevent destructive repository file deletion.
- Added mktemp usage for secure temporary deb file downloads in nvidia.sh, heroic.sh, and tools.sh to eliminate TOCTOU vulnerabilities in /tmp.
- Fixed Bluetooth USB dongle misclassification as WiFi devices by excluding "bluetooth" strings from USB_WIFI_DEVS detection in firmware.sh.
- Properly utilized the need array for selective package installation in internet.sh instead of hardcoding full package list.
- Corrected fwupdmgr duplicate execution and grep false positives in system.sh with strict pattern matching for available updates.
- update docs and added quickstart guide

modules/gpu/nvidia.sh

@@ -21,18 +21,20 @@ _enable_cuda_repo() {
         if dpkg -s cuda-keyring &>/dev/null; then
             return 0 # ya instalado → su .list ya existe
         fi
+        local tmp_deb
+        tmp_deb=$(mktemp "${TMPDIR:-/tmp}/cuda-keyring.XXXXXX.deb") || return 1
         if ! wget -q "https://developer.download.nvidia.com/compute/cuda/repos/debian13/x86_64/cuda-keyring_1.1-1_all.deb" \
-            -O /tmp/cuda-keyring.deb; then
-            rm -f /tmp/cuda-keyring.deb
+            -O "$tmp_deb"; then
+            rm -f "$tmp_deb"
             _msg "CUDA Repo — Error" "Failed to download cuda-keyring.\n\nNo NVIDIA driver was installed." 10 60
             return 1
         fi
-        if ! sudo dpkg -i /tmp/cuda-keyring.deb; then
-            rm -f /tmp/cuda-keyring.deb
+        if ! sudo dpkg -i "$tmp_deb"; then
+            rm -f "$tmp_deb"
             _msg "CUDA Repo — Error" "Failed to install cuda-keyring.\n\nNo NVIDIA driver was installed." 10 60
             return 1
         fi
-        rm -f /tmp/cuda-keyring.deb
+        rm -f "$tmp_deb"
         return 0
     fi