feat: add ai investigation assistant for incident analysis

[Mkalbani]

closes #140

• Implement InvestigationService with context generation capabilities
• Add related event suggestions using correlation scoring
• Build chronological timeline analysis for incidents
• Extract indicators of compromise automatically
• Suggest investigation steps based on severity levels
• Add comprehensive test suite with 24 test cases
• Update Jest config to include root-level src tests
• Provide TypeScript interfaces for all data structures

Description

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Related Issues

Fixes #
Related to #

Changes Made

Testing

• I have tested these changes locally
• Tests pass locally (npm run test)
• Linting passes (npm run lint)
• Code is formatted (npm run format)
• TypeScript builds successfully (npm run build)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests passed with my changes