Add end-to-end integration tests for deposit and withdraw flows

[robertocarlous]

Summary

Deposit and withdraw are the most financially sensitive flows but only have unit-level coverage. Full integration tests against a real Postgres + mocked Stellar RPC would catch regressions that unit tests miss.

Scope

• Seed test database with a funded user and custodial wallet
• POST /api/deposit: verify Transaction record, position update, event cursor advance
• POST /api/withdraw: verify balance deduction, transaction record, DLQ on RPC failure
• Assert correct HTTP status, response shape, and database state after each operation

Acceptance Criteria

• Tests run against a Dockerised Postgres (can use existing docker-compose)
• Stellar RPC calls are mocked via jest.mock
• Both happy path and error path (RPC failure → DLQ) covered
• Tests added to CI node-ci.yml workflow

[DeveloperEmmy]

@DeveloperEmmy has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello and good day, please can I work on this issue

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Congratulations, @DeveloperEmmy! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

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