chore(deps): upgrade to Python 3.12 and prepare for 0.6.0 release

- Update Docker base image to Python 3.12-slim-bookworm
- Bump version from 0.6.0rc1 to 0.6.0
- Update documentation to reflect release version changes
- Fix license specification in pyproject.toml and setup.py
- Clean up code formatting in demo_docker_api.py

BREAKING CHANGE: Base Python version upgraded from 3.10 to 3.12

setup.py

@@ -49,13 +49,12 @@ setup(
     url="https://github.com/unclecode/crawl4ai",
     author="Unclecode",
     author_email="unclecode@kidocode.com",
-    license="MIT",
+    license="Apache-2.0",
     packages=find_packages(),
     package_data={"crawl4ai": ["js_snippet/*.js"]},
     classifiers=[
         "Development Status :: 3 - Alpha",
         "Intended Audience :: Developers",
-        "License :: OSI Approved :: Apache Software License",
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.9",
         "Programming Language :: Python :: 3.10",