feat(helm): HPA for app deployment (toggleable, CPU-based)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

helm/ezscale-website/templates/hpa-app.yaml

@@ -0,0 +1,23 @@
+{{- if .Values.app.autoscaling.enabled }}
+apiVersion: autoscaling/v2
+kind: HorizontalPodAutoscaler
+metadata:
+  name: {{ include "ezscale-website.fullname" . }}-app
+  labels:
+    {{- include "ezscale-website.labels" . | nindent 4 }}
+    app.kubernetes.io/component: app
+spec:
+  scaleTargetRef:
+    apiVersion: apps/v1
+    kind: Deployment
+    name: {{ include "ezscale-website.fullname" . }}-app
+  minReplicas: {{ .Values.app.autoscaling.minReplicas }}
+  maxReplicas: {{ .Values.app.autoscaling.maxReplicas }}
+  metrics:
+    - type: Resource
+      resource:
+        name: cpu
+        target:
+          type: Utilization
+          averageUtilization: {{ .Values.app.autoscaling.targetCPU }}
+{{- end }}