feat(outline): Add support for generating structured commit messages with bullet points

[vowstar]

• Add OutlineCommand to handle structured commit message generation
• Implement build_outline_prompt method in AIPrompt for structured messages
• Update CLI and main logic to support the outline command
• Add outline method in LumenProvider to process structured commit requests

Example:

# Generate a structured commit message with bullet points
lumen outline
# Output:
# feat(button.tsx): Update button color to align with brand identity guidelines
#
# - Update primary button color to match new brand color scheme
# - Add hover state color transition for better user feedback
# - Update color variables in theme configuration for consistency