chore(release): bump version to 2.4.0

Version bump for the v2.4.0 release. Release notes attached to the tag
once this lands.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: MarkusNeusinger

pyproject.toml

@@ -1,7 +1,7 @@
 # pyproject.toml
 [project]
 name = "anyplot"
-version = "2.3.0"
+version = "2.4.0"
 description = "AI-powered plotting examples"
 authors = [{ name = "Markus Neusinger", email = "admin@anyplot.ai" }]
 requires-python = ">=3.13"