feat: migrate cert-manager from Terraform to ArgoCD (#42)

- Add cert-manager base ArgoCD application with namespace, RBAC resources
- Create cert-manager overlay for au-syd1 with Helm chart configuration
- Update platform ApplicationSet to include cert-manager deployment
- Configure cert-manager v1.19.2 with jetstack Helm repository
- Maintain one-to-one migration from Terraform configuration

Reviewed-on: #42

argocd/applicationsets/platform.yaml

@@ -13,6 +13,7 @@ spec:
       - path: apps/overlays/*/artifactapi
       - path: apps/overlays/*/cattle-system
       - path: apps/overlays/*/certificates
+      - path: apps/overlays/*/cert-manager
       - path: apps/overlays/*/reflector-system
       - path: apps/overlays/*/reloader-system
       - path: apps/overlays/*/jfrog

argocd/projects/platform.yaml

@@ -11,11 +11,14 @@ spec:
     - oci://ghcr.io/emberstack/helm-charts
     - oci://ghcr.io/woodpecker-ci/helm/woodpecker
     - https://releases.rancher.com/server-charts/stable
+    - https://charts.jetstack.io
   destinations:
     - namespace: '*-system'
       server: https://kubernetes.default.svc
     - namespace: 'artifactapi'
       server: https://kubernetes.default.svc
+    - namespace: 'cert-manager'
+      server: https://kubernetes.default.svc
     - namespace: 'certificates'
       server: https://kubernetes.default.svc
     - namespace: 'jfrog'
@@ -33,6 +36,10 @@ spec:
       kind: ClusterRoleBinding
     - group: 'apiextensions.k8s.io'
       kind: CustomResourceDefinition
+    - group: 'admissionregistration.k8s.io'
+      kind: MutatingWebhookConfiguration
+    - group: 'admissionregistration.k8s.io'
+      kind: ValidatingWebhookConfiguration
     - group: 'scheduling.k8s.io'
       kind: PriorityClass
   namespaceResourceWhitelist: