refactor: drop Incus, add Podman + Quadlets

modules/common/podman.nix

@@ -0,0 +1,22 @@
+{ config, lib, pkgs, ... }:
+{
+  virtualisation.podman = {
+    enable = true;
+    # Rootless containers by default
+    # No daemon — systemd + quadlets manage everything
+  };
+
+  # Quadlet support — .container files in /etc/containers/systemd/
+  virtualisation.quadlet.enable = true;
+
+  # Nix-declared containers
+  virtualisation.oci-containers = {
+    backend = "podman";
+    containers = {
+      nginx-example = {
+        image = "nginx:latest";
+        ports = [ "9999:80" ];
+      };
+    };
+  };
+}