Add Helm chart and production Kubernetes docs

[jusso-dev]

Problem

Docker Compose is good for local installs, but many self-hosters will deploy monitoring infrastructure on Kubernetes.

Scope

• Add Helm chart for API, worker, optional Playwright worker, Postgres/Redis dependencies or external references, Prometheus ServiceMonitor, and ingress.
• Document production configuration, secrets, database migrations, backups, scaling workers, and rolling upgrades.
• Add values for resource requests/limits and pod disruption budgets.
• Provide example manifests for common ingress controllers.

Acceptance criteria

• Helm install can deploy a working stack into a local Kubernetes cluster.
• Chart supports external Postgres and Redis.
• Migrations run in a controlled job or documented process.
• Prometheus scraping can be enabled through values.
• Docs cover upgrade and backup expectations.

Notes

This issue is part of the GoUpTime product roadmap.