feat: add marketplace metrics, privacy features, and service registry endpoints

- Add Prometheus metrics for marketplace API throughput and error rates with new dashboard panels
- Implement confidential transaction models with encryption support and access control
- Add key management system with registration, rotation, and audit logging
- Create services and registry routers for service discovery and management
- Integrate ZK proof generation for privacy-preserving receipts
- Add metrics instru

apps/zk-circuits/README.md

@@ -0,0 +1,170 @@
+# AITBC ZK Circuits
+
+Zero-knowledge circuits for privacy-preserving receipt attestation in the AITBC network.
+
+## Overview
+
+This project implements zk-SNARK circuits to enable privacy-preserving settlement flows while maintaining verifiability of receipts.
+
+## Quick Start
+
+### Prerequisites
+
+- Node.js 16+
+- npm or yarn
+
+### Installation
+
+```bash
+cd apps/zk-circuits
+npm install
+```
+
+### Compile Circuit
+
+```bash
+npm run compile
+```
+
+### Generate Trusted Setup
+
+```bash
+# Start phase 1 setup
+npm run setup
+
+# Contribute to setup (run multiple times with different participants)
+npm run contribute
+
+# Prepare phase 2
+npm run prepare
+
+# Generate proving key
+npm run generate-zkey
+
+# Contribute to zkey (optional)
+npm run contribute-zkey
+
+# Export verification key
+npm run export-verification-key
+```
+
+### Generate and Verify Proof
+
+```bash
+# Generate proof
+npm run generate-proof
+
+# Verify proof
+npm run verify
+
+# Run tests
+npm test
+```
+
+## Circuit Design
+
+### Current Implementation
+
+The initial circuit (`receipt.circom`) implements a simple hash preimage proof:
+
+- **Public Inputs**: Receipt hash
+- **Private Inputs**: Receipt data (job ID, miner ID, result, pricing)
+- **Proof**: Demonstrates knowledge of receipt data without revealing it
+
+### Future Enhancements
+
+1. **Full Receipt Attestation**: Complete validation of receipt structure
+2. **Signature Verification**: ECDSA signature validation
+3. **Arithmetic Validation**: Pricing and reward calculations
+4. **Range Proofs**: Confidential transaction amounts
+
+## Development
+
+### Circuit Structure
+
+```
+receipt.circom          # Main circuit file
+├── ReceiptHashPreimage # Simple hash preimage proof
+├── ReceiptAttestation  # Full receipt validation (WIP)
+└── ECDSAVerify        # Signature verification (WIP)
+```
+
+### Testing
+
+```bash
+# Run all tests
+npm test
+
+# Run specific test
+npx mocha test.js
+```
+
+### Integration
+
+The circuits integrate with:
+
+1. **Coordinator API**: Proof generation service
+2. **Settlement Layer**: On-chain verification contracts
+3. **Pool Hub**: Privacy options for miners
+
+## Security
+
+### Trusted Setup
+
+The Groth16 setup requires a trusted setup ceremony:
+
+1. Multi-party participation (>100 recommended)
+2. Public documentation
+3. Destruction of toxic waste
+
+### Audits
+
+- Circuit formal verification
+- Third-party security review
+- Public disclosure of circuits
+
+## Performance
+
+| Metric | Value |
+|--------|-------|
+| Proof Size | ~200 bytes |
+| Prover Time | 5-15 seconds |
+| Verifier Time | 3ms |
+| Gas Cost | ~200k |
+
+## Troubleshooting
+
+### Common Issues
+
+1. **Circuit compilation fails**: Check circom version and syntax
+2. **Setup fails**: Ensure sufficient disk space and memory
+3. **Proof generation slow**: Consider using faster hardware or PLONK
+
+### Debug Commands
+
+```bash
+# Check circuit constraints
+circom receipt.circom --r1cs --inspect
+
+# View witness
+snarkjs wtns check witness.wtns receipt.wasm input.json
+
+# Debug proof generation
+DEBUG=snarkjs npm run generate-proof
+```
+
+## Resources
+
+- [Circom Documentation](https://docs.circom.io/)
+- [snarkjs Documentation](https://github.com/iden3/snarkjs)
+- [ZK Whitepaper](https://eprint.iacr.org/2016/260)
+
+## Contributing
+
+1. Fork the repository
+2. Create feature branch
+3. Submit pull request with tests
+
+## License
+
+MIT