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/services/default.nix

@@ -0,0 +1,65 @@
+{ pkgs, ... }:
+
+{
+  # Сервер OpenSSH с усиленной безопасностью
+  services.openssh = {
+    enable = true;
+
+    settings = {
+      # Аутентификация
+      PasswordAuthentication = false;
+      PubkeyAuthentication = true;
+      PermitRootLogin = "no";
+      KbdInteractiveAuthentication = false;
+      ChallengeResponseAuthentication = false;
+      PermitEmptyPasswords = false;
+
+      # Сессии и доступ
+      LoginGraceTime = 30;
+      MaxAuthTries = 3;
+      MaxSessions = 2;
+      ClientAliveInterval = 300;
+      ClientAliveCountMax = 2;
+
+      # Отключить устаревшие возможности
+      X11Forwarding = false;
+      AllowAgentForwarding = false;
+      PermitUserEnvironment = false;
+    };
+
+    # Дополнительная конфигурация
+    extraConfig = ''
+      # Authentication methods
+      AuthenticationMethods publickey
+
+      # Reduce legacy or risky features
+      IgnoreRhosts yes
+      HostbasedAuthentication no
+      TCPKeepAlive no
+
+      # Connection throttling
+      MaxStartups 10:30:60
+    '';
+  };
+
+  # Агент GnuPG
+  programs.gnupg.agent = {
+    enable = true;
+    enableSSHSupport = true;
+  };
+
+  # MTR для сетевой диагностики
+  programs.mtr.enable = true;
+
+  # Firefox
+  programs.firefox.enable = true;
+
+  # AmneziaVPN
+  programs.amnezia-vpn.enable = true;
+
+  # Системные пакеты
+  environment.systemPackages = with pkgs; [
+    amneziawg-tools
+    neofetch
+  ];
+}