Create comprehensive .junie/guidelines.md for AI agent configuration

Created detailed guidelines document for AI agents (like Junie) with:
- Complete project architecture overview
- SOLID principles and code quality standards
- DTO/Transformer patterns with examples
- Testing standards and export testing rules
- Database/Model conventions
- Filament resource best practices
- Export system architecture and queue configuration
- Security and multi-tenancy guidelines
- Development workflow commands
- Performance optimization strategies
- Common pitfalls to avoid
- Code review checklist
- Documentation references and learning resources

This provides maximum information for AI agents to understand the codebase structure, conventions, and performance requirements.

Co-authored-by: nielsdrost7 <[email protected]>

Author: Copilot