feat: Add BIP39 seed builder and DLC message type compliance

[bennyhodl]

Summary

• Added BIP39 mnemonic support to the Builder with a new SeedConfig enum
• Made DLC messages spec-compliant by including type numbers in serialization
• Extended seed bytes from 32 to 64 bytes to support BIP39 seed format

Changes

Seed Builder Enhancement

• Introduced SeedConfig enum with three options:
  • Random: Generate a random seed
  • Mnemonic(String, String): Use BIP39 mnemonic with optional passphrase
  • Bytes([u8; 64]): Direct byte input
• Extended seed size from 32 to 64 bytes throughout the codebase to support BIP39's seed format

DLC Message Type Compliance

• Added types.rs module with all DLC message type constants
• Modified impl_dlc_writeable! macro to include type IDs in serialization
• Each message type now writes its type ID as the first field when serializing
• Ensures compliance with DLC specification for message format