feat: add Amplitude telemetry to quickstart template Dockerfiles

[ytallo]

Summary

The Amplitude Metrics PRD requires telemetry env vars to be added to all team-maintained Dockerfiles in the quickstart templates.

Changes needed

Add ENV III_CONTAINER=docker and ENV III_ENV=development to:

• templates/iii/quickstart/services/client/Dockerfile
• templates/iii/quickstart/services/compute-service/Dockerfile
• templates/iii/quickstart/services/data-service/Dockerfile
• templates/iii/quickstart/services/payment-service/Dockerfile

Add III_HOST_USER_ID pass-through to the iii service in:

• templates/iii/quickstart/docker-compose.yaml

environment:
  - III_HOST_USER_ID=${III_HOST_USER_ID:-}

Why

• III_CONTAINER=docker tells the engine telemetry it's running in a container (authoritative signal over heuristics).
• III_ENV=development sets the environment context for telemetry.
• III_HOST_USER_ID allows correlating container events back to the host developer in Amplitude dashboards.

Reference

See iii-hq/amplitude-metrics PRD, section 5 (Docker Files).