Replace Aura consensus signatures with ML-DSA-44 in Substrate #40

Goal

Modify the Aura consensus implementation in the Substrate framework to replace the current classical signature scheme (sr25519) with a post-quantum signature scheme (ML-DSA-44).

Scope

• analyze the current Aura consensus code and identify all places where sr25519 is used for signing and verification
• replace the existing signature flow with ML-DSA-44
• update related key handling, signature verification, and consensus message processing if required
• ensure compatibility of the modified implementation across the Aura workflow

Expected outcome

• Aura consensus no longer relies on sr25519 signatures
• signing and verification are performed using ML-DSA-44
• the codebase is updated and ready for further testing and integration