lang & firefox-esr

- Added `_detect_lang()` helper to `modules/utils.sh` (extracts first 2 chars from `$LANG`, fallback to `en`).
- Created `_detect_lang_pkg()` utility for LibreOffice localization: handles regional variants (`es-ar` → `es`) and skips English packages.
- Implemented `_check_network()` with cascade methods (ping→wget→curl) in `modules/utils.sh`. Warning-only pre-flight check after `check_sudo` in `debianito.sh`, compatible with `set -euo pipefail`.
- Fixed system time validation: changed `2026` threshold to `2025` in `check_system_time()` (replaced self-referential `$(date +%Y)` which always evaluated false).
- Refactored LibreOffice language selection in `office.sh`: replaced 10 lines of inline logic with `_detect_lang_pkg "libreoffice-l10n"`.
- Overhauled Firefox ESR integration in `internet.sh`: added state detection, mutual exclusion guard (both Firefox variants selected → warning), new `install_firefox_esr()` function with language support.
- Updated `install_firefox_mozilla()`: added Debian version guard (`<12`), replaced `_run_install` with `_run_cmd`.
- Standardized header in internet menu and improved whiptail UX for Firefox options.

docs/zram.md

@@ -241,3 +241,11 @@ To ensure ZRAM persists across reboots, the script writes configuration to `/etc
 ```bash
 echo "zram" | sudo tee /etc/modules-load.d/zram.conf
 ```
+
+
+### References:
+
+- [https://docs.kernel.org/admin-guide/blockdev/zram.html](https://docs.kernel.org/admin-guide/blockdev/zram.html)
+- [https://wiki.debian.org/ZRam](https://wiki.debian.org/ZRam)
+- [https://wiki.archlinux.org/title/Zram](https://wiki.archlinux.org/title/Zram)
+- [https://wiki.gentoo.org/wiki/Zram](https://wiki.gentoo.org/wiki/Zram)