Docs: Docker + PostgreSQL setup, client routing options, and deployment diagrams

[joeldickson]

Summary

Addresses #9 by expanding setup and deployment documentation for Docker and PostgreSQL, plus clearer client connection guidance.

What changed

• Updated README.md with:
  • Docker Hub image usage (agoda/devex-telemetry)
  • docker compose quick-start
  • PostgreSQL configuration notes (including current MVP EnsureCreated() behavior and migration-path note)
  • Improved Pointing Clients at Your Deployment section
    • Preferred DNS approach using default client host http://compilation-metrics
    • Workstation override via DEVFEEDBACK_URL
    • IT-managed rollout note
• Added docs/deployment-scenarios.md
  • Multiple deployment topologies
  • Mermaid diagrams
  • Client routing behavior and environment variable examples
  • Basic security notes
• Linked README to the new deployment scenarios doc

Why

• Make first-time setup and production-ish rollout paths clearer
• Document how clients should be pointed at deployments for both small and large orgs
• Provide visual deployment references for faster onboarding and infra discussions

Notes

• This PR is docs-only; no runtime code changes.