fix: Use setuptools-scm for automatic version management from git tags

Replace hardcoded versions with setuptools-scm to automatically derive
package version from git tags. This fixes the PyPI publishing issue where
the dist file wasn't updating according to the tag name.

Changes:
- Add setuptools-scm to build dependencies in pyproject.toml
- Configure dynamic version using git tags
- Update __init__.py to read version from package metadata
- Remove obsolete setup.py with hardcoded version

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

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

Author: andrzejnovak

mkdocs_header_dropdown/__init__.py

@@ -1,3 +1,11 @@
 from .plugin import HeaderDropdownPlugin
 
-__version__ = "0.1.0"
+try:
+    from importlib.metadata import version, PackageNotFoundError
+except ImportError:
+    from importlib_metadata import version, PackageNotFoundError
+
+try:
+    __version__ = version("mkdocs-header-dropdown")
+except PackageNotFoundError:
+    __version__ = "unknown"

pyproject.toml

@@ -1,10 +1,10 @@
 [build-system]
-requires = ["setuptools>=45", "wheel"]
+requires = ["setuptools>=45", "setuptools-scm>=8", "wheel"]
 build-backend = "setuptools.build_meta"
 
 [project]
 name = "mkdocs-header-dropdown"
-version = "0.1.0"
+dynamic = ["version"]
 description = "A MkDocs plugin to add configurable dropdown menus to the Material theme header"
 readme = "README.md"
 requires-python = ">=3.7"
@@ -51,3 +51,6 @@ include-package-data = true
 
 [tool.setuptools.package-data]
 mkdocs_header_dropdown = ["templates/**/*"]
+
+[tool.setuptools_scm]
+local_scheme = "no-local-version"