Replace GRANDPA consensus signatures with ML-DSA-44 in Substrate

[kostiask]

Goal

Modify the GRANDPA consensus implementation in the Substrate framework to replace the current classical signature scheme (sr25519 -> 'ed25519') with a post-quantum signature scheme (ML-DSA-44).

Scope

• analyze the GRANDPA consensus code and identify all places where sr25519 is used
• replace signature generation and verification with ML-DSA-44
• update vote signing, justification handling, and finality logic if required
• ensure compatibility of the modified implementation within the GRANDPA workflow

Expected outcome

• GRANDPA consensus no longer relies on sr25519 ( 'ed25519')

• all signatures are generated and verified using ML-DSA-44

• consensus finality mechanism works correctly with the new signature scheme

• Discovery & Audit

• ML-DSA-44 Integration

• Generic Signature Trait

• Primitives Refactor (sp-consensus-grandpa)

• Client Logic Refactor (sc-consensus-grandpa)

• Frame Integration Refactor

• Testing & Benchmarking