feat: add Gitea credentials and Actions runner

- Add gitea-creds ExternalSecret for ArgoCD authentication to Gitea
- Enable Gitea Actions in helm-values.yaml
- Add gitea-runner deployment for CI/CD

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

gitea-runner/manifests/runner-secret.yaml

@@ -0,0 +1,18 @@
+apiVersion: external-secrets.io/v1
+kind: ExternalSecret
+metadata:
+  name: gitea-runner-secret
+  namespace: gitea
+spec:
+  refreshInterval: 1h
+  secretStoreRef:
+    kind: ClusterSecretStore
+    name: vault-backend
+  target:
+    name: gitea-runner-secret
+    creationPolicy: Owner
+  data:
+    - secretKey: token
+      remoteRef:
+        key: gitea
+        property: runner_token