Add core infrastructure to GitOps: providers, external-dns

- providers.yaml: Crossplane provider installations
- provider-configs.yaml: Provider authentication configs
- external-dns.yaml: Automatic DNS record management

Testing batch deployment before adding more components.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

kustomization.yaml

@@ -2,7 +2,12 @@ apiVersion: kustomize.config.k8s.io/v1beta1
 kind: Kustomization
 
 resources:
-# Start with just core files for GitOps testing
+# Core infrastructure
+- providers.yaml
+- provider-configs.yaml
+- external-dns.yaml
+
+# Applications
 - forgejo-k8s.yaml
 - pomerium.yaml
 - vaultwarden.yaml