Localize external-secrets for ringtail (amd64) via nix build

container.py builds arm64 (indri/Dagger); add default.nix to build the amd64
image on ringtail's nix-container-builder (Go 1.26, -tags all_providers).
external-secrets-ringtail now uses a thin overlay over the shared manifest,
overriding only the image to the -nix tag. Repoints the app at the overlay.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

containers/external-secrets/default.nix

@@ -0,0 +1,56 @@
+# Nix-built External Secrets Operator (amd64, for ringtail k3s).
+# Builds v2.2.0 from the forge mirror with all secret providers compiled in,
+# faithful to upstream's `make build` (-tags all_providers). The container.py
+# sibling builds the arm64 image for indri's minikube; this default.nix builds
+# the amd64 image on ringtail's nix-container-builder.
+{ pkgs ? import <nixpkgs> { } }:
+
+let
+  version = "2.2.0";
+
+  src = pkgs.fetchgit {
+    url = "https://forge.ops.eblu.me/mirrors/external-secrets.git";
+    rev = "v${version}";
+    hash = "sha256-eAocOAp5s4CFRrpKfQr2lf3Ji+6nQQ1A5/eTw5B7v9U=";
+  };
+
+  # external-secrets v2.2.0 requires Go >= 1.26.1; nixpkgs default go is 1.25.x.
+  external-secrets = (pkgs.buildGoModule.override { go = pkgs.go_1_26; }) {
+    inherit src version;
+    pname = "external-secrets";
+    vendorHash = "sha256-0xuBK3fjAplPLAElHvKB6d+2lDz+De/s91fV4dPZwjE=";
+
+    doCheck = false;
+
+    subPackages = [ "." ];
+
+    tags = [ "all_providers" ];
+
+    ldflags = [ "-s" "-w" ];
+
+    meta = with pkgs.lib; {
+      description = "Kubernetes operator that integrates external secret management systems";
+      homepage = "https://github.com/external-secrets/external-secrets";
+      license = licenses.asl20;
+      mainProgram = "external-secrets";
+    };
+  };
+in
+
+pkgs.dockerTools.buildLayeredImage {
+  name = "blumeops/external-secrets";
+  contents = [
+    external-secrets
+    pkgs.cacert
+    pkgs.tzdata
+  ];
+
+  config = {
+    Entrypoint = [ "${external-secrets}/bin/external-secrets" ];
+    Env = [
+      "SSL_CERT_FILE=${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt"
+      "TZDIR=${pkgs.tzdata}/share/zoneinfo"
+    ];
+    User = "65534";
+  };
+}