feat(fonts): add install-fonts command for XeLaTeX projects

[prudhomm]

Summary

Add an install-fonts command to download and set up fonts required for XeLaTeX-based presentations and documents.

Changes

New Module: fonts.py

• FontInstaller class for downloading and extracting font zip files
• Support for progress indication during downloads
• Default font sources: Marianne (French government font) and Roboto Mono
• Idempotent installation (skips existing fonts unless --force is used)
• List installed fonts and font files

Configuration: config.py

• Added get_fonts_config() method for font configuration
• New [fonts] section in sample config template:

  [tool.article-cli.fonts]
  directory = "fonts"
  
  [[tool.article-cli.fonts.sources]]
  name = "Marianne"
  url = "https://www.systeme-de-design.gouv.fr/uploads/Marianne_fd0ba9c190.zip"

CLI: cli.py

• Added install-fonts command with options:
  • --dir: Custom installation directory (default: fonts/)
  • --force: Re-download even if fonts already exist
  • --list: List installed fonts instead of installing

Usage

# Install all configured fonts
article-cli install-fonts

# Install to specific directory
article-cli install-fonts --dir custom-fonts/

# Force re-download
article-cli install-fonts --force

# List installed fonts
article-cli install-fonts --list

Testing

• Added 18 comprehensive tests for font installation
• All 89/91 tests pass (2 pre-existing environment-related failures)

Closes #4