FEATURE: allow artifacts to be updated

[SamSaffron]

Add support for versioned artifacts with improved diff handling

• Add versioned artifacts support allowing artifacts to be updated and tracked

  • New ai_artifact_versions table to store version history
  • Support for updating artifacts through a new UpdateArtifact tool
  • Add version-aware artifact rendering in posts
  • Include change descriptions for version tracking

• Enhance artifact rendering and security

  • Add support for module-type scripts and external JS dependencies
  • Expand CSP to allow trusted CDN sources (unpkg, cdnjs, jsdelivr, googleapis)
  • Improve JavaScript handling in artifacts

• Implement robust diff handling system (this is dormant but ready to use once LLMs catch up)

  • Add new DiffUtils module for applying changes to artifacts
  • Support for unified diff format with multiple hunks
  • Intelligent handling of whitespace and line endings
  • Comprehensive error handling for diff operations

• Update routes and UI components

  • Add versioned artifact routes
  • Update markdown processing for versioned artifacts

Also

• Tweaks summary prompt
• Improves upload support in custom tool to also provide urls