Add type hints to Python SDK examples

[sunilp]

Summary

The Python examples in examples/python_sdk/ work but lack type hints. Adding type hints improves readability and enables IDE support for developers using LDP.

What to do

1. Add type hints to all functions in:
   • examples/python_sdk/ldp_delegate.py
   • examples/python_sdk/ldp_client.py
   • examples/python_sdk/multi_delegate_routing.py
2. Use TypedDict or dataclass for LDP message structures
3. Ensure the examples still run correctly after changes

Acceptance criteria

• All function signatures have type hints
• LDP data structures use TypedDict or dataclass
• python ldp_delegate.py and python ldp_client.py still work