Bump version to v2.3.0b4

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: michaelchu

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "optopsy"
-version = "2.3.0b3"
+version = "2.3.0b4"
 description = "A nimble backtesting and statistics library for options strategies"
 readme = "README.md"
 license = "AGPL-3.0-or-later"