Create chapter 9 folder structure with template files

[Copilot]

This PR implements the requested structure for chapter 9:

• Created a folder called 09-lesson under the lessons directory
• Added the following subdirectories:
  • assets for lesson images and other resources
  • solution containing placeholder solution files
  • translations for future language translations
• Created a README.md with the same headers and formatting as existing lessons
• Added styles.css to maintain consistency with other lessons

The README.md follows the same structure as other lessons, including:

• Title and learning objectives
• Setup instructions
• Related resources section
• Placeholder sections for narrative and technical content
• Assignment and solution sections
• Knowledge check and self-study resources

This provides a template that can be populated with actual content when the chapter material is developed.

Fixes #119.

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