feat: add hpa support

[gjorgji-ts]

Motivation

HPA managed deployments were being scaled down by LightsOut but the HPA would immediately fight back, restoring replicas to minReplicas. The original approach of setting minReplicas=0 was invalid. Kubernetes only allows minReplicas=0 with Object or External metrics, Resource (CPU) metrics are rejected by the API server.

Changes

Rather than patching minReplicas, LightsOut now sets spec.behavior.scaleUp.selectPolicy: Disabled on HPAs that target a managed workload. This prevents the HPA from acting while LightsOut holds the deployment at 0, without requiring any specific metric type configuration.

Strategy:

• Downscale: read the current scaleUp.selectPolicy, store it in an annotation (lightsout.techsupport.mk/original-hpa-scale-up-policy), then set selectPolicy: Disabled
• Upscale: restore the original policy (or remove the field if it was absent) and remove the LightsOut annotations
• Skip conditions: HPAs already at selectPolicy: Disabled without a managed-by annotation are treated as user-managed and left untouched, HPAs managed by a different schedule are skipped

Testing

• Unit tests: internal/controller/hpa_test.go (patch/restore logic, skip conditions, policy preservation), internal/controller/scaler_test.go (HPA wired into scale-down/up paths for Deployments and StatefulSets, crash window recovery)
• e2e: test/e2e/hpa_test.go — 5 scenarios run against a live cluster:
  1. Downscale sets selectPolicy: Disabled, leaves minReplicas unchanged
  2. Upscale restores original policy and removes annotations
  3. Workload without an HPA scales normally (no HPA-related side effects)
  4. User-managed HPA with selectPolicy: Disabled already set is skipped (no annotations stamped)
  5. v1 HPA (autoscaling/v1) is handled correctly via internal v2 storage
• Manual: verified against local Kind demo — api-server HPA correctly enters ScalingDisabled state with pods at 0, then fully restores on upscale

Checklist

• Tests added / updated
• Docs updated if behaviour changed
• make lint passes
• make test passes
• make manifests generate run if API types changed
• make helm-crds run if CRDs changed