feat(dev): add Docker Compose for Postgres and update Quick Start docs (closes #4)

[arkagrawall]

This PR introduces a minimal docker-compose.yml for local Postgres 15 and updates the Quick Start docs to prefer docker compose over a one-off docker run.

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✅ What’s included

• New docker-compose.yml with a db service:
  • Postgres 15
  • Dev-friendly credentials
  • Persistent named volume
  • Healthcheck for service readiness
• README.md updates:
  • Option A (Docker Compose, recommended)
  • Option B (one-off container, original method preserved)
  • Notes for stopping and cleaning up the database

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💡 Why

• Simplifies onboarding for contributors — one command to start Postgres
• Keeps backwards compatibility (existing docker run instructions remain)
• No changes to how the API, UI, or Verifier bot run locally
• Connection strings and app startup remain the same

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🛠 How to use

# Start Postgres
docker compose up -d db

# Apply migrations (unchanged)
cd UnsecuredAPIKeys.WebAPI
dotnet ef database update --project ../UnsecuredAPIKeys.Data --startup-project .

# Run apps (unchanged)

# API
cd UnsecuredAPIKeys.WebAPI && dotnet run

# UI
cd ../UnsecuredAPIKeys.UI && npm install && npm run dev

# Verifier Bot
cd ../UnsecuredAPIKeys.Bots.Verifier && dotnet run

Default endpoints:

• UI → http://localhost:3000
• API → http://localhost:7227
• API Docs → http://localhost:7227/scalar/v1

---

📌 Notes

• docker compose down will stop the database.
• Use docker compose down -v if you also want to remove the persistent volume.

Closes #4

[pavannitheesh]

when i run this command
-> dotnet ef database update --project ../UnsecuredAPIKeys.Data --startup-project .
i am getting a postgres password authentication problem.
how to solve this