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

infra/traefik-routes/manifests/gitea-ssh.yaml

@@ -0,0 +1,14 @@
+# Gitea SSH access via Traefik TCP routing (port 2222)
+apiVersion: traefik.io/v1alpha1
+kind: IngressRouteTCP
+metadata:
+  name: gitea-ssh
+  namespace: gitea
+spec:
+  entryPoints:
+    - ssh
+  routes:
+    - match: HostSNI(`*`)
+      services:
+        - name: gitea-ssh
+          port: 22