feat(api): expose deployment events on detail responses

[ctxswitch]

Parent

Related to #1

What to build

Expose Deployment Events on detail responses so on-call engineers can see what happened to a Deployment Request over time.

Acceptance criteria

• GET /deployments/{id} includes Deployment Events in the detail response.
• GET /deployments continues to omit full event history.
• Event fields are serialized consistently.
• Tests cover event visibility on detail responses and event omission from list responses.

Blocked by

• feat(api): fetch deployment request details #6
• feat(domain): record deployment events #7