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/USER_GUIDE.md

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+# User Guide - ISO-20022 Combo Flow
+
+## Getting Started
+
+### Creating Your First Plan
+
+1. **Navigate to Builder**
+   - Click "Builder" in the navigation menu
+   - You'll see the adapter palette on the left and canvas on the right
+
+2. **Add Steps**
+   - Drag adapters from the palette to the canvas
+   - Steps will be added in order
+   - You can reorder steps by dragging them
+
+3. **Configure Steps**
+   - Click "Edit" on any step to configure parameters
+   - Fill in required fields (amount, asset, beneficiary, etc.)
+   - Check compliance requirements for fiat steps
+
+4. **Review & Sign**
+   - Click "Review & Sign" when your plan is complete
+   - Review the plan summary
+   - Sign with your Web3 wallet
+
+5. **Execute**
+   - Click "Create Plan" to register the plan
+   - Click "Execute Plan" to start execution
+   - Monitor progress in the execution timeline
+
+---
+
+## Step Types
+
+### Borrow
+- Borrow digital assets using collateral
+- Configure: Asset, Amount, Collateral Reference
+
+### Swap
+- Exchange one asset for another
+- Configure: From Asset, To Asset, Amount
+- Shows estimated slippage
+
+### Repay
+- Repay borrowed assets
+- Configure: Asset, Amount
+
+### Pay
+- Send fiat payment via banking rails
+- Configure: Asset, Amount, Beneficiary IBAN
+- Requires compliance (LEI/DID/KYC/AML)
+
+---
+
+## Compliance
+
+### Required Information
+- **LEI**: Legal Entity Identifier
+- **DID**: Decentralized Identifier
+- **KYC**: Know Your Customer verification
+- **AML**: Anti-Money Laundering check
+
+### Setting Up Compliance
+1. Go to Settings page
+2. Enter your LEI and DID
+3. Complete KYC/AML verification
+4. Compliance status will be shown in the dashboard
+
+---
+
+## Simulation (Advanced Users)
+
+### Enable Simulation
+1. Toggle "Enable Simulation" in preview page
+2. Click "Run Simulation"
+3. Review results:
+   - Gas estimates
+   - Slippage analysis
+   - Liquidity checks
+   - Warnings and errors
+
+---
+
+## Troubleshooting
+
+### Plan Validation Errors
+- Check recursion depth (max 3)
+- Verify step dependencies
+- Ensure amounts are positive
+
+### Execution Failures
+- Check wallet connection
+- Verify sufficient balance
+- Review error messages in timeline
+
+### Compliance Issues
+- Update compliance information in Settings
+- Verify KYC/AML status
+- Check expiration dates
+
+---
+
+**Last Updated**: 2025-01-15
+