Add Chaum-Pedersen proof example

[tob-joe]

Overview

Add an example demonstrating Chaum-Pedersen proof: proving equality of discrete logarithms across two bases (h1 = g1^x AND h2 = g2^x).

Requirements

• Should use Ristretto255 with proper Inscribe wrappers for domain separation
• Should implement individual proof verification with Fiat-Shamir via Decree
• Should implement batch verification with proper Fiat-Shamir (committing to all proofs before deriving coefficients)
• Should include improper batch verification example that derives coefficients incrementally as each proof is added
• Should include tests for soundness and demonstrating the adaptive attack enabled by the improper approach

Should demonstrate proper use of Inscribe trait for composite structures and secure batch verification patterns.