docs: add comprehensive CLAUDE.md guide for AI assistants (#116)

Add detailed documentation covering:
- Project architecture and directory structure
- Development environment setup and workflows
- Service architecture and dependency injection patterns
- React component development with custom hooks
- Testing guidelines and build processes
- Git workflow and coding conventions
- Common tasks and troubleshooting

This guide provides AI assistants with comprehensive context
about the GRID codebase structure, patterns, and best practices.

Co-authored-by: Claude <noreply@anthropic.com>

Author: millsydotdev