Sync Python SDK with current Engine API

[VivekChaurasia03]

Summary

• align SDK authentication, routes, parameters, and defaults with the current Engine API documentation
• add the missing point-conditions and tropical-cyclone tracker functions
• add webhook endpoint and subscription management for all nine documented webhook operations
• fix archived initialization-time returns, station forecast routing, sounding filters, and predicted-path lookup
• expose derived forecast variables documented in windborne/engine#1017
• update the README and developer guide, incorporating the review feedback from Fix README_dev.md link for PyPI #18
• bump the package version to 1.7.0

Testing

• python -m unittest discover -s tests -v (24 tests)
• python compileall for the package and tests
• built windborne-1.7.0-py3-none-any.whl with uv
• imported the built wheel and verified the new public webhook API

Scope

This PR updates the Python package first. CLI parity will follow separately after the SDK surface is reviewed.