fix: encrypt/decrypt list title tags for private lists

[barrydeen]

Summary

• Add title tag support to NIP-51 follow sets and bookmark sets
• For private lists, the title is encrypted inside the content alongside member/item tags
• For public lists, the title is included as a public tag
• Parsing now extracts title from public tags or decrypted content, falling back to the d tag
• Fixed a bug where creating a private list sent empty unencrypted content instead of properly encrypting

Test plan

• Create a new private follow set — verify the name displays correctly
• Create a new public follow set — verify the name displays correctly
• Add/remove members from a private list — verify the name persists
• Restart the app and verify list names load correctly from relays
• Check lists created by other clients display readable names