Refactor testing infrastructure to use test containers and fixtures

[Smartdevs17]

Context

Tests need isolated environments with proper fixtures.

Current Limitation

Tests share database with no fixture management.

Expected Outcome

• Test containers for isolation
• Fixture factories for test data
• Snapshot testing
• Parallel test execution

Acceptance Criteria

• Docker test containers
• Fixture factories for all models
• API response snapshot testing
• Parallel test execution
• Test data seeding
• Coverage reporting with thresholds
• Flaky test detection

Technical Scope

• jest.config.js - Test configuration
• jest.backend.config.js - Backend test config
• backend/tests/ - Backend tests
• e2e/ - E2E tests

[bitcoindev817-hue]

@bitcoindev817-hue has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

I'm a full-stack developer and I'd like to take this issue.
I understand the requirements and will follow the existing project structure, keep the implementation clean, and include proper tests where applicable.

ETA: 1–3 days (depending on scope)

ℹ️ Repo Maintainers: To accept this application, review their application or assign @bitcoindev817-hue to this issue.

[drips-wave]

Congratulations, @bitcoindev817-hue! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @bitcoindev817-hue: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[drips-wave]

This issue has been completed by @bitcoindev817-hue as part of the Stellar Wave Program's 7th Wave 🥳

😎 @bitcoindev817-hue: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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