feat: SOPS + age encrypted secrets structure

- .sops.yaml with 3 age keys (admin, dev, prod)
- infra/gitea/values/*.enc.yaml — per-env encrypted Helm values
- infra/kargo/values/*.enc.yaml — per-env encrypted Kargo admin secrets
- kargo/credentials/*.enc.yaml — per-env encrypted git credentials (ksops)
- infra/kargo-credentials/ — ArgoCD app for deploying Kargo creds via ksops
- All repoURLs point to deploy-app-kargo-private

Structure from deploy-app-kargo (reference), adapted for SOPS workflow

kargo/infra/verification/rbac.yaml

@@ -0,0 +1,27 @@
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: kargo-verifier
+  namespace: infra
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: kargo-verifier-infra
+rules:
+  - apiGroups: [""]
+    resources: ["pods"]
+    verbs: ["get", "list"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: kargo-verifier-infra
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: kargo-verifier-infra
+subjects:
+  - kind: ServiceAccount
+    name: kargo-verifier
+    namespace: infra