Enhance ComboHandler and orchestrator functionality with access control and error handling improvements

- Added AccessControl to ComboHandler for role-based access management.
- Implemented gas estimation for plan execution and improved gas limit checks.
- Updated execution and preparation methods to enforce step count limits and role restrictions.
- Enhanced error handling in orchestrator API endpoints with AppError for better validation feedback.
- Integrated request timeout middleware for improved request management.
- Updated Swagger documentation to reflect new API structure and parameters.

docs/DEVELOPER_ONBOARDING.md

@@ -0,0 +1,104 @@
+# Developer Onboarding Guide
+
+## Prerequisites
+
+- Node.js 18+
+- npm or yarn
+- Git
+- Docker (optional)
+- PostgreSQL (for local development)
+- Redis (optional, for caching)
+
+## Setup
+
+### 1. Clone Repository
+
+```bash
+git clone https://github.com/your-org/CurrenciCombo.git
+cd CurrenciCombo
+```
+
+### 2. Frontend Setup
+
+```bash
+cd webapp
+npm install
+cp .env.example .env.local
+# Edit .env.local with your configuration
+npm run dev
+```
+
+### 3. Backend Setup
+
+```bash
+cd orchestrator
+npm install
+cp .env.example .env
+# Edit .env with your configuration
+npm run migrate
+npm run dev
+```
+
+### 4. Smart Contracts Setup
+
+```bash
+cd contracts
+npm install
+npm run compile
+npm run test
+```
+
+## Development Workflow
+
+### Making Changes
+
+1. Create a feature branch: `git checkout -b feature/your-feature`
+2. Make changes
+3. Run tests: `npm test`
+4. Lint code: `npm run lint`
+5. Commit: `git commit -m "feat: your feature"`
+6. Push: `git push origin feature/your-feature`
+7. Create Pull Request
+
+### Code Style
+
+- TypeScript for all new code
+- Follow ESLint configuration
+- Use Prettier for formatting
+- Write JSDoc comments for public APIs
+
+### Testing
+
+- Write unit tests for utilities
+- Write integration tests for API endpoints
+- Write E2E tests for user flows
+- Maintain >80% code coverage
+
+## Project Structure
+
+```
+CurrenciCombo/
+├── webapp/           # Next.js frontend
+├── orchestrator/     # Express backend
+├── contracts/        # Smart contracts
+└── docs/            # Documentation
+```
+
+## Key Concepts
+
+- **Plans**: Multi-step financial workflows
+- **Steps**: Individual operations (borrow, swap, repay, pay)
+- **2PC**: Two-phase commit for atomic execution
+- **Compliance**: LEI/DID/KYC/AML requirements
+
+## Getting Help
+
+- Check documentation in `docs/`
+- Review code comments
+- Ask questions in team chat
+- File issues for bugs
+
+---
+
+**Last Updated**: 2025-01-15
+