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>

infrastructure/cert-manager/cluster-issuer.yaml

@@ -0,0 +1,31 @@
+apiVersion: cert-manager.io/v1
+kind: ClusterIssuer
+metadata:
+  name: selfsigned-issuer
+spec:
+  selfSigned: {}
+---
+apiVersion: cert-manager.io/v1
+kind: Certificate
+metadata:
+  name: infinicaretech-ca
+  namespace: cert-manager
+spec:
+  isCA: true
+  commonName: infinicaretech-ca
+  secretName: infinicaretech-ca-secret
+  privateKey:
+    algorithm: ECDSA
+    size: 256
+  issuerRef:
+    name: selfsigned-issuer
+    kind: ClusterIssuer
+    group: cert-manager.io
+---
+apiVersion: cert-manager.io/v1
+kind: ClusterIssuer
+metadata:
+  name: infinicaretech-ca-issuer
+spec:
+  ca:
+    secretName: infinicaretech-ca-secret