chore: update Nix configurations for Nixcloud and common hosts

- Add Nixcloud host configurations including networking, hardware, and system settings
- Refactor existing configurations for clarity and organization
- Remove unused podman configuration from home-manager
- Update SSH agent settings and session variables in Nixbook host

hosts/common/default.nix

@@ -72,6 +72,7 @@
   programs = {
     gnupg = {
       agent = {
+        enableSSHSupport = true;
         enable = true;
         pinentryPackage = pkgs.pinentry-tty;
       };
@@ -89,6 +90,7 @@
     pcscd.enable = true;
     # xserver.displayManager.sessionCommands =
     #   "${pkgs.xorg.xmodmap}/bin/xmodmap -e 'keycode 64 = Alt_L'";
+
     udev.packages = [
       pkgs.libwacom
       pkgs.nitrokey-udev-rules