Optimize unit tests: nip44.spec.ts (cryptography)

[phoenix-server]

The nip44.spec.ts suite (23 tests) performs expensive elliptic-curve cryptography using secp256k1:

• Key generation per test
• secp256k1 encryption/decryption operations
• Repeated verification overhead

Goal: Reduce execution time by at least 30% through key reuse patterns and operation consolidation.