feat: add comprehensive NixOS configuration documentation and structure

- Introduced `08-structure.md` detailing project structure, main files, and versioning.
- Created `README.md` for documentation overview and quick start guide.
- Added user-specific configurations for Alacritty, Vim, Micro, Git, Zsh, Tmux, and tools.
- Implemented system modules for desktop environment (KDE Plasma), audio (PipeWire), networking, and services (OpenSSH, GnuPG).
- Configured Nix settings with flakes support and garbage collection.
- Established user management for `ada` with necessary groups and shell settings.
- Enabled VirtualBox guest additions for improved VM experience.

nixos/modules/system/locale.nix

@@ -0,0 +1,21 @@
+{ ... }:
+
+{
+  # Часовой пояс
+  time.timeZone = "Europe/Moscow";
+
+  # Интернационализация
+  i18n.defaultLocale = "en_US.UTF-8";
+
+  i18n.extraLocaleSettings = {
+    LC_ADDRESS = "ru_RU.UTF-8";
+    LC_IDENTIFICATION = "ru_RU.UTF-8";
+    LC_MEASUREMENT = "ru_RU.UTF-8";
+    LC_MONETARY = "ru_RU.UTF-8";
+    LC_NAME = "ru_RU.UTF-8";
+    LC_NUMERIC = "ru_RU.UTF-8";
+    LC_PAPER = "ru_RU.UTF-8";
+    LC_TELEPHONE = "ru_RU.UTF-8";
+    LC_TIME = "ru_RU.UTF-8";
+  };
+}