Description

Implement storage of chat conversations on Nostr using nip44 encryption, similar to how API keys and lightning invoices are currently stored.

Requirements

• Use nip44 encryption for secure conversation storage
• Follow the existing pattern used for API keys and lightning invoices
• Ensure conversations are properly encrypted and decrypted
• Maintain compatibility with current chat functionality

Acceptance Criteria

• Chat conversations are stored on Nostr relays
• nip44 encryption is properly implemented
• Conversations can be retrieved and decrypted correctly
• No breaking changes to existing chat functionality
• Proper error handling for encryption/decryption failures

Technical Notes

Reference the existing implementation for API keys and lightning invoices to maintain consistency in the codebase.