[FEATURE] Helm sizing values #3692

Add per-workload replicas, resources and pdb values to the stage charts, with today's defaults, where null leaves the field unset so another owner can manage it.

Tracks "Add Helm sizing values" in the Operator Supplied Values workstream of the Extensible Install Roadmap.

Required changes

• The values shape from the sizing contract ([FEATURE] Add Sizing Contract for --component based sizing (kustomize) #3168): apiServer, idpServer, controller, atelet, router, egress, podcertController, postgres. The install chart passes them through.
• A values-large.yaml matching sizing-large.
• The schema ([FEATURE] Generate values.schema.json from ate-setup's settings registry #3683) enforces types.
• Postgres storage values follow the immutability guard ([FEATURE] Refuse Postgres storage size or class changes the cluster cannot apply #3691).

Dependencies: #3682; the list of fields that may be unmanaged (#3168).

Enforcement: default values render the same as sizing-default, and values-large.yaml renders the same as sizing-large. A null value omits the field.

Parent Issue: #3165