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

ci/gitea-runner/manifests/runner.yaml

@@ -0,0 +1,79 @@
+# Gitea Actions runner (act_runner)
+# Requires registration token in gitea-runner-token secret
+# Token is generated in Gitea admin → Actions → Runners → Create new runner
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: gitea-runner-config
+  namespace: gitea-runner
+data:
+  config.yaml: |
+    log:
+      level: info
+    runner:
+      file: .runner
+      capacity: 1
+      timeout: 3h
+      labels:
+        - "ubuntu-latest:docker://node:20-bullseye"
+        - "ubuntu-22.04:docker://node:20-bullseye"
+    cache:
+      enabled: true
+      dir: ""
+    container:
+      network: ""
+      privileged: false
+      options:
+      workdir_parent:
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: gitea-runner
+  namespace: gitea-runner
+  labels:
+    app: gitea-runner
+spec:
+  replicas: 0  # Set to 1 after creating registration token
+  selector:
+    matchLabels:
+      app: gitea-runner
+  template:
+    metadata:
+      labels:
+        app: gitea-runner
+    spec:
+      containers:
+        - name: runner
+          image: gitea/act_runner:0.2.11
+          env:
+            - name: GITEA_INSTANCE_URL
+              value: "http://gitea-http.gitea.svc.cluster.local:3000"
+            - name: GITEA_RUNNER_REGISTRATION_TOKEN
+              valueFrom:
+                secretKeyRef:
+                  name: gitea-runner-token
+                  key: token
+                  optional: true
+          volumeMounts:
+            - name: config
+              mountPath: /config
+              readOnly: true
+            - name: data
+              mountPath: /data
+          resources:
+            requests:
+              cpu: 100m
+              memory: 128Mi
+            limits:
+              cpu: "2"
+              memory: 2Gi
+      volumes:
+        - name: config
+          configMap:
+            name: gitea-runner-config
+        - name: data
+          emptyDir: {}
+      nodeSelector:
+        node-role.kubernetes.io/worker: ""