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

pyproject.toml

@@ -8,7 +8,7 @@ dynamic = ["version"]
 description = "🚀🤖 Crawl4AI: Open-source LLM Friendly Web Crawler & scraper"
 readme = "README.md"
 requires-python = ">=3.9"
-license = {text = "Apache-2.0"}
+license = "Apache-2.0"
 authors = [
     {name = "Unclecode", email = "unclecode@kidocode.com"}
 ]
@@ -48,7 +48,6 @@ dependencies = [
 classifiers = [
     "Development Status :: 4 - Beta",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: Apache Software License",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",