Add critical module code coverage thresholds

[nanaf6203-bit]

Establish minimum coverage gating for core modules.

Acceptance Criteria:

• Thresholds are defined for auth, users, properties, and transactions.
• CI fails when thresholds are not met.
• Thresholds are documented.
• Existing tests are reviewed for baseline coverage.

[nafiuishaaq]

@nafiuishaaq has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Let me professionally implement this task with precision and as apt with an ETA of 2 to 4 hours

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

[drips-wave]

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

🧑‍💻 @nafiuishaaq: 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

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