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

.github/PULL_REQUEST_TEMPLATE/rfc.md

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+## RFC Type
+- [ ] Protocol (P)
+- [ ] API (A)
+- [ ] Ecosystem (E)
+- [ ] Governance (G)
+- [ ] Network (N)
+
+## Required Information
+
+**RFC Number**: _Assigned by maintainers_
+
+**Title**: _Clear and descriptive title_
+
+**Authors**: _GitHub usernames, comma separated_
+
+**Status**: Draft
+
+**Start Date**: YYYY-MM-DD
+
+**Summary**
+
+_One-paragraph summary of the proposal. What is being changed and why?_
+
+## Motivation
+
+_Why is this change needed? What problem does it solve? Who are the stakeholders?_
+
+## Detailed Design
+
+_Provide a comprehensive technical specification. Include:_
+
+- Architecture diagrams (if applicable)
+- API changes
+- Data model changes
+- Protocol modifications
+- Implementation details
+
+## Rationale and Alternatives
+
+_Why this approach over alternatives? What other approaches were considered?_
+
+## Impact
+
+_Effects on existing systems:_
+
+- Breaking changes
+- Migration requirements
+- Backward compatibility
+- Ecosystem impact
+
+## Security Considerations
+
+_Security implications and mitigations:_
+
+- Attack vectors
+- Privacy implications
+- Audit requirements
+- Compliance considerations
+
+## Testing Strategy
+
+_How will this be tested?_
+
+- Unit tests
+- Integration tests
+- Security audits
+- Performance testing
+- Testnet deployment
+
+## Unresolved Questions
+
+_Open issues to be resolved:_
+
+- Technical questions
+- Implementation concerns
+- Dependencies
+- Timeline considerations
+
+## Implementation Plan
+
+_Timeline and milestones:_
+
+- Phase 1: [description] - [date]
+- Phase 2: [description] - [date]
+- Phase 3: [description] - [date]
+
+## Checklist
+
+- [ ] I have read the [RFC Process](https://aitbc.io/rfc-process)
+- [ ] I have searched for existing RFCs to avoid duplicates
+- [ ] I have discussed this idea in a GitHub issue first
+- [ ] I have addressed all required sections
+- [ ] I have considered security implications
+- [ ] I have included a testing strategy
+- [ ] I am prepared to respond to feedback
+- [ ] I understand this is a public document
+
+## Additional Context
+
+_Any additional information, links, or references that help reviewers understand the proposal._
+
+---
+
+### Review Process
+
+1. **Initial Review** (2 weeks minimum)
+   - Technical review by core team
+   - Community feedback period
+   - Security assessment
+
+2. **Final Comment Period** (10 days)
+   - Last call for objections
+   - All issues must be addressed
+   - Decision finalization
+
+3. **Decision**
+   - Accepted: Implementation begins
+   - Rejected: Documented with reasoning
+   - Deferred: Returned for revisions
+
+### Review Guidelines
+
+- Provide constructive, technical feedback
+- Consider ecosystem impact
+- Suggest improvements and alternatives
+- Be respectful and professional
+
+### Resources
+
+- [RFC Process Documentation](https://aitbc.io/rfc-process)
+- [Active RFCs](https://aitbc.io/active-rfcs)
+- [Community Guidelines](https://aitbc.io/community)
+- [Security Guidelines](https://aitbc.io/security)