chore: bump version to 0.1.0b2 (#10)

## Summary

- Bumps version from `0.1.0b1` to `0.1.0b2`

## Test plan

- [ ] All CI checks pass
- [ ] After merge: tag `v0.1.0b2` and create GitHub pre-release

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: tommed

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "nexa-marketdata"
-version = "0.1.0b1"
+version = "0.1.0b2"
 description = "Unified API client for European power market data sources"
 authors = ["Phase Nexa <hello@phasenexa.com>"]
 readme = "README.md"