Act as a Chief Information Security Officer (CISO) for a large government agency. Create a comprehensive migration roadmap to transition all existing cryptographic systems to post-quantum cryptography (PQC) standards. Your plan must include an inventory of current cryptographic assets (RSA, ECC), a risk assessment timeline based on estimates regarding the arrival of cryptographically relevant quantum computers (CRQCs), and a phased implementation strategy. Detail the hybrid encryption approaches required during the transition period to ensure backward compatibility. Discuss the impact on hardware security modules (HSMs) and key management lifecycle practices.