test: end-to-end smoke test for core P2P flow

[bbkenny]

This PR adds a comprehensive end-to-end smoke test for the core P2P trading lifecycle.

The test covers:

• Trade creation by buyer.
• Trade locking by seller.
• Trade reveal by seller (after cash receipt).
• Secret retrieval by seller.
• Trade completion by buyer (on-chain release simulation).

I've also added fast-check to the API dependencies to support future property-based testing and fixed the existing test environment.

Closes #72

[bbkenny]

Hi @ericmt-98, I've implemented a comprehensive end-to-end smoke test for the core P2P flow as requested in issue #72. The test simulates the entire lifecycle from trade creation to completion. I also cleaned up the test environment and added fast-check for future property-based testing. Ready for review!

[drips-wave]

@bbkenny Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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