chore: move create use example to specs crate

[SHAcollision]

Fixes #278

This example can now be run from the specs crate https://github.com/pubky/pubky-app-specs/blob/main/examples/create_user.rs

For tests to work you need a working neo4j and redis instance with the example dataset in docker/db-graph

• Testing: Implement and pass new tests for the new features/fixes, cargo test.
• Performance: Ensure new code has relevant performance benchmarks, cargo bench