feat: add beat and worker-usage Helm deployments

[MSami625]

Summary

• Add beat Deployment (Celery Beat + platform queue worker, single replica)
• Add worker-usage Deployment (usage queue, threads pool)
• Helm unit tests, docs, kind-deploy rollout waits, GKE overlay resources

Test plan

• make unittest (46 passed)

[greptile-apps]

Greptile Summary

The PR adds dedicated Helm deployments for Celery Beat/platform work and usage-queue processing, including autoscaling support and lifecycle handling.

• Adds single-replica Beat and platform-worker process supervision with graceful signal forwarding.
• Adds a worker-usage Deployment and CPU HorizontalPodAutoscaler.
• Extends chart defaults, tests, documentation, deployment scripts, and the GKE overlay for both components.
• Updates the chart version and CI Helm version.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains.

Important Files Changed

Filename	Overview
charts/efficientai/templates/_helpers.tpl	Adds default commands for the supervised Beat/platform processes and the dedicated usage worker; the previously reported supervision and signal-forwarding issues are addressed.
charts/efficientai/templates/beat/deployment.yaml	Adds the single-replica Beat Deployment with configurable scheduling, pod settings, resources, and termination grace period.
charts/efficientai/templates/worker-usage/deployment.yaml	Adds the usage-queue worker Deployment and correctly delegates replica management when autoscaling is enabled.
charts/efficientai/templates/worker-usage/hpa.yaml	Adds the previously missing autoscaler and targets the worker-usage Deployment consistently.
charts/efficientai/tests/beat_deployment_test.yaml	Covers Beat rendering, supervision command content, configuration overrides, disablement, and the single-replica constraint.
charts/efficientai/tests/worker_usage_deployment_test.yaml	Covers usage-worker command rendering, overrides, enablement, replica omission, and HPA creation.
charts/efficientai/values.yaml	Defines defaults and customization surfaces for the Beat and worker-usage components.

_{Reviews (4): Last reviewed commit: "feat: implement graceful shutdown for Ce..." | Re-trigger Greptile}