feat: initial GitOps infrastructure

ArgoCD app definitions, Kustomize manifests for health-app,
cert-manager ClusterIssuer, and AppProject configuration.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/health-app.yaml

@@ -0,0 +1,31 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: health-app
+  namespace: argocd
+  finalizers:
+    - resources-finalizer.argocd.argoproj.io
+spec:
+  project: infinicaretech
+  source:
+    repoURL: https://github.com/infinicaretech/gitops-infra.git
+    targetRevision: main
+    path: environments/health-app/overlays/production
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: health-app
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true
+      allowEmpty: false
+    syncOptions:
+      - CreateNamespace=true
+      - PrunePropagationPolicy=foreground
+      - PruneLast=true
+    retry:
+      limit: 3
+      backoff:
+        duration: 5s
+        factor: 2
+        maxDuration: 3m0s