ci: align Python version support to 3.13 only

- Update CI/CD workflows to test only Python 3.13
- Remove Python 3.11 and 3.12 from test matrix
- Update package classifiers to reflect Python 3.13 only support
- Align with requires-python = '>=3.13' constraint

pyproject.toml

@@ -135,8 +135,6 @@ classifiers = [
     "Development Status :: 4 - Beta",
     "Intended Audience :: Developers",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.11",
-    "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Operating System :: OS Independent",
     "Topic :: Software Development :: Libraries :: Python Modules",