feat: space management command feature

[Goddhi]

• guppy key create - Generate Ed25519 keypairs with multibase encoding
• guppy key whoami - Display current key DID
• guppy space create - Create new spaces with local private key generation
• guppy space ls - List all spaces with registration status
• guppy space use - Switch current active space
• guppy space info [name] - Display space details
• guppy space whoami - Show current space
  Space Registration:
• guppy space register - Generate UCAN delegations for manual registration
• guppy space delegate - Create delegations without registration state

@temi0x will implement registerSpaceWithService() function to enable automatic space registration. This requires:

Service API integration using existing access/authorize + access/claim patterns
Direct delegation submission to Storacha service instead of file export
Automated email verification polling
Real-time registration status verification