Add Docker example for one-command delegate setup

[sunilp]

Summary

Add a Dockerfile and docker-compose example so anyone can run an LDP delegate with a single command — no Python setup required.

What to do

1. Create Dockerfile at repo root that packages the Python SDK delegate
2. Create examples/docker/ with:
   • docker-compose.yml running 3 delegates with different profiles (fast, balanced, deep)
   • demo_delegate.py — a simple delegate using LdpDelegate
   • README.md with setup instructions
3. One command to start: docker compose up
4. One command to demo: python examples/demo_smart_routing.py (against the running delegates)

Why this matters

Docker is the fastest path from "I saw this on GitHub" to "I'm running it." It removes all friction: no Python version issues, no dependency conflicts, no port management. A2A has Docker examples for their samples.

Acceptance criteria

• docker build -t ldp-delegate . works
• docker compose up starts 3 delegates with different identity profiles
• The smart routing demo can connect to them and show the routing comparison
• README with copy-paste instructions

[dagangtj]

I'll work on this issue. ETA: 24 hours.

[sunilp]

Hey @dagangtj, thanks for picking this up! Just checking in — it's been a few days since your comment. How's progress going? Let us know if you've hit any blockers or need any guidance. Happy to help!