[Testing] Raise backend coverage back to 60% and restore thresholds

[ogazboiz]

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Why this matters

The backend coverage thresholds in backend/vitest.config.ts were 60% (added in #373) but the suite only covers ~50% of lines/statements and ~46% of functions, so the coverage gate failed every CI run regardless of test outcomes. As a stopgap the thresholds were lowered to a ratchet floor at current coverage so CI is green and can't regress. This issue tracks adding tests to climb back to 60% and restoring the thresholds.

Acceptance criteria

• Add unit/integration tests to raise backend coverage to >= 60% statements, functions, and lines
• Restore thresholds in backend/vitest.config.ts to 60 across the board
• npx vitest run --coverage passes with the 60% thresholds
• Prioritize the least-covered areas (controllers, services, workers)

Files to touch

• backend/vitest.config.ts (restore thresholds)
• new/expanded tests under backend/tests/ and backend/src/__tests__/

Out of scope

• Frontend or contract coverage

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[devonahi]

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Congratulations, @devonahi! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @devonahi: 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.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

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This issue has been completed by @devonahi as part of the Stellar Wave Program's 5th Wave 🥳

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