Implement Profile Migration Mechanism Between Nodes

[filinvadim]

We need to implement a secure and user-friendly mechanism that allows a user to migrate their profile (including identity, contacts, settings, and content) from one node to another.

This is essential for:

• Device changes (e.g. switching computers),
• Backup and recovery,
• Node reinstallation or rehosting.

Requirements:

1. Export:

• Identity keys (public/private),
• User data (name, bio, avatar, etc.),
• Contacts/follows,
• Posts, messages, settings.

2. Securely encrypt the export file with a user-defined passphrase.
3. Import:

• Validate data integrity and signature,
• Restore all profile data on the new node,
• Optionally notify old peers or previous node (if reachable) of migration.

Security:

• Prevent replay attacks or double imports.
• Allow verification that a migration was initiated by the real user (e.g. signed intent).

Make user migration possible without manual database copy. This is essential for long-term usability and resilience of the WarpNet ecosystem.