Wire NVCA otel-collector to event-ledger

Description

nvca-otel-collector isn't wired up to publish to event-ledger yet.

Definition of Done

• applyPSATIdentity's nvca-token volume is mounted into the nvca-otel-collector init container (currently only mounted into the agent container).
• A distinct env var points at the token path, used in otel_collector_config.yaml in place of ${env:NGC_SERVICE_API_KEY_FILE}.
• getOTelCollectorAuthConfig's OAuth2 branch has an explicit self-hosted override.
• clusterConfig.fndService.serviceURL points at event-ledger.
• global.nvcaOperator.selfManaged.otelCollector.enabled defaults to false in deploy/stacks/nvcf-compute-plane/environments/base.yaml.

Depends on #1655 (event-ledger accepting NVCA's PSAT).