refactor: reorganize directory structure (variants -> hw, glue -> fleet)

- Rename variants/ to hw/ for clearer hardware module naming
- Rename glue/ to fleet/ for more intuitive fleet management
- Move boot/fs configuration from glue/boot.nix to separate fleet/boot.nix and fleet/fs.nix
- Improve separation of concerns between boot, filesystem, and common config

fleet/boot.nix

@@ -0,0 +1,48 @@
+# ============================================================================
+# Boot configuration module
+# ============================================================================
+# This module defines:
+# - Bootloader configuration (systemd-boot with Plymouth)
+# - Timezone and locale settings
+# - Systemd sleep configuration
+
+{ config, lib, ... }:
+{
+  boot = {
+    loader.systemd-boot.enable = lib.mkDefault true;
+    loader.efi.canTouchEfiVariables = lib.mkDefault true;
+    plymouth.enable = lib.mkDefault true;
+
+    # Enable "Silent boot"
+    consoleLogLevel = 3;
+    initrd.verbose = false;
+
+    # Hide the OS choice for bootloaders.
+    # It's still possible to open the bootloader list by pressing any key
+    # It will just not appear on screen unless a key is pressed
+    loader.timeout = lib.mkDefault 0;
+  };
+
+  # Set your time zone.
+  time.timeZone = "America/New_York";
+
+  # Select internationalisation properties.
+  i18n.defaultLocale = "en_US.UTF-8";
+
+  i18n.extraLocaleSettings = {
+    LC_ADDRESS = "en_US.UTF-8";
+    LC_IDENTIFICATION = "en_US.UTF-8";
+    LC_MEASUREMENT = "en_US.UTF-8";
+    LC_MONETARY = "en_US.UTF-8";
+    LC_NAME = "en_US.UTF-8";
+    LC_NUMERIC = "en_US.UTF-8";
+    LC_PAPER = "en_US.UTF-8";
+    LC_TELEPHONE = "en_US.UTF-8";
+    LC_TIME = "en_US.UTF-8";
+  };
+
+  systemd.sleep.extraConfig = ''
+    SuspendState=freeze
+    HibernateDelaySec=2h
+  '';
+}