Use importlib.metadata for single version source of truth

Version is now read from package metadata (set in pyproject.toml)
instead of being hardcoded in two places. Only pyproject.toml needs
to be updated at release time.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: tpellissier

src/PowerPlatform/Dataverse/__version__.py

@@ -3,4 +3,9 @@
 
 """Version information for PowerPlatform-Dataverse-Client package."""
 
-__version__ = "0.1.0b5"
+from importlib.metadata import version, PackageNotFoundError
+
+try:
+    __version__ = version("PowerPlatform-Dataverse-Client")
+except PackageNotFoundError:
+    __version__ = "0.0.0.dev0"