Add UN/CEFACT reference data model compliance documentation

[Prasiejames]

Problem

The project tokenizes Real-World Assets but has no documentation mapping its data model to regulatory standards like UN/CEFACT (United Nations Centre for Trade Facilitation and Electronic Business) or the relevant securities regulation frameworks.

Expected Behavior

A docs/compliance/ directory with documents explaining:

1. How the contract data model maps to UN/CEFACT Buy-Ship-Pay reference data model
2. KYC/AML compliance approach (levels, expiry, provider tracking)
3. Securities law considerations (accredited investor checks, transfer restrictions)
4. Jurisdiction-specific considerations (EU MiCA, US SEC regs, UAE VARA, etc.)

Proposed Solution

Create the following documents:

• docs/compliance/un-cefact-mapping.md — Maps contract types to UN/CEFACT semantics
• docs/compliance/securities-regulation.md — How the contract features address regulatory requirements
• docs/compliance/kyc-aml.md — KYC architecture and provider model

This documentation is essential for institutional adoption and regulatory review.