docs: NICo logging - reference docs

[akorobkov-nvda]

How would you describe the priority of this documentation request

Critical (currently preventing usage)

Describe the future/missing documentation

Summary

Document NICo logging and provide a portable centralized-logging reference, completing the logging part of #1989

Deliverables

1. docs/observability/logging.md covering: where NICo logs, the log format/schema, how to tune levels (incl. runtime changes) and how to centralize logs

Acceptance criteria

• From the doc alone, an operator can find where logs go, the format and how to set levels (including per-component differences)
• A working collector example ships logs from a NICo pod to a backend

Out of scope

• Changing any component's log format or levels in source. Need to be a separate issue

Related / see also

• feat: Expose BMC/DPU logs through centralized logging ref. arch #1990 - BMC/DPU logs through centralized logging ref. arch
• feat: Reduce noise in carbide-api logs (with two examples) #2048 - Logs noise filtering
• feat(logging): add a component field to log metadata #2354 - Add a component field to log metadata

Code of Conduct

• I agree to follow NCX Infra Controller's Code of Conduct
• I have searched the open documentation issues and have found no duplicates for this documentation issue