feat(packs): opt-in package packs — media/office/dev/gaming/containers/compat

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/packs/containers.nix

@@ -0,0 +1,43 @@
+# Containers pack — Docker + Podman.
+#
+# Unifies the docker config that was previously split between core.nix
+# (basic enable + weekly autoPrune) and development.nix (daemon.settings
+# buildkit + registry-mirror + autoPrune --all), plus the podman block
+# that lived coding-gated in development.nix. Now a single source of truth
+# gated on omni.packs.containers.enable. (The merged result is the union
+# of the two old blocks — identical on any host that had both features on,
+# e.g. omni.)
+{ config, lib, ... }:
+let
+  cfg = config.omni.packs.containers;
+in
+{
+  options.omni.packs.containers.enable =
+    lib.mkEnableOption "Containers pack (Docker + Podman)";
+
+  config = lib.mkIf cfg.enable {
+    virtualisation.docker = {
+      enable = true;
+      enableOnBoot = true;
+      daemon.settings = {
+        features = {
+          buildkit = true;
+        };
+        registry-mirrors = [ "https://mirror.gcr.io" ];
+      };
+
+      autoPrune = {
+        enable = true;
+        dates = "weekly";
+        flags = [ "--all" ];
+      };
+    };
+
+    # Podman as Docker alternative (dockerCompat off to avoid conflict).
+    virtualisation.podman = {
+      enable = true;
+      dockerCompat = false;
+      defaultNetwork.settings.dns_enabled = true;
+    };
+  };
+}