docs: add Docker mesh observability example

[SeCuReDmE-main-dev]

PR: Add Docker mesh observability and sensitive-source isolation example

Linked Issue

Refs #362

Summary

This PR adds a docs-only example for running multiple CodeProject.AI Server containers in a Docker mesh while keeping persistent volumes, private workload networks, and observability boundaries explicit.

The page covers TCP/UDP 32168, KnownMeshHostnames, named volumes, Docker labels, optional metadata-only observability, and sensitive-source logging guidance.

Scope

Included:

• Docker mesh example page under docs/;
• validation checklist;
• sensitive-source safety section.

Excluded:

• no server code changes;
• no module changes;
• no new dependencies;
• no default telemetry;
• no behavior changes.

Validation

Commands run:

docker compose config --quiet

Endpoint checks:

http://localhost:33168 -> HTTP 200
http://localhost:33268 -> HTTP 200
http://localhost:33368 -> HTTP 200

Network check:

Datadog Agent is attached to studycase-observability-private and not attached to studycase-cpai-mesh.

Known Risks

• Docker network behavior can vary across Docker Desktop, Linux, WSL, and bridged networks.
• Observability examples must stay metadata-only and avoid raw payload logging.

Reviewer Notes

• This is documentation only.
• The observability section is optional and vendor-neutral.
• If maintainers prefer, the observability section can be split into a follow-up.