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/gaming/heroic.sh

@@ -2,7 +2,8 @@
 # Heroic Games Launcher installation from GitHub releases
 
 install_heroic() {
-    local heroic_deb="/tmp/heroic.deb"
+    local heroic_deb
+    heroic_deb=$(mktemp "${TMPDIR:-/tmp}/heroic-XXXXXX.deb") || return 1
     local ua="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
 
     _run_cmd "Heroic" "sudo apt install -y curl jq" "Installing dependencies..."
@@ -24,7 +25,7 @@ install_heroic() {
         return 1
     fi
 
-    _run_cmd "Heroic" "curl -sL -H 'User-Agent: $ua' -o '$heroic_deb' '$deb_url'" "Downloading Heroic..."
+    _run_cmd "Heroic" "curl -fsSL -H 'User-Agent: $ua' -o '$heroic_deb' '$deb_url'" "Downloading Heroic..."
 
     if ! dpkg-deb --info "$heroic_deb" >/dev/null 2>&1; then
         _msg "Heroic Error" "Downloaded .deb is corrupted or truncated.\n\nRemoving file." 10 60

modules/gaming/tools.sh

@@ -36,7 +36,8 @@ install_openrgb() {
             ;;
     esac
 
-    local deb_path="/tmp/openrgb.deb"
+    local deb_path
+    deb_path=$(mktemp "${TMPDIR:-/tmp}/openrgb-XXXXXX.deb") || return 1
     local ua="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
 
     _run_cmd "OpenRGB" "sudo apt install -y curl jq" "Installing dependencies..."
@@ -62,7 +63,7 @@ install_openrgb() {
         return 1
     fi
 
-    _run_cmd "OpenRGB" "curl -L -o '${deb_path}' -A '${ua}' '${deb_url}'" "Downloading OpenRGB..."
+    _run_cmd "OpenRGB" "curl -fsSL -o '${deb_path}' -A '${ua}' '${deb_url}'" "Downloading OpenRGB..."
 
     if [ -n "$sha256" ]; then
         if ! echo "$sha256  $deb_path" | sha256sum -c --strict; then