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>

environments/health-app/base/networkpolicy.yaml

@@ -0,0 +1,21 @@
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: health-app-netpol
+spec:
+  podSelector:
+    matchLabels:
+      app.kubernetes.io/name: health-app
+  policyTypes:
+    - Ingress
+    - Egress
+  ingress:
+    - from:
+        - namespaceSelector:
+            matchLabels:
+              kubernetes.io/metadata.name: ingress-nginx
+      ports:
+        - port: 3000
+          protocol: TCP
+  egress:
+    - {}