Implement certificate expiry and validity period support

[AnnabelJoe]

Description

Some regulatory frameworks require certificates to have a validity period (e.g., 12 months from generation). Expiry support should be added to the certificate model.

Acceptance Criteria

• Certificate has optional expiry_date field
• Expired certificates shown as expired in UI
• Expired certificates cannot be retired
• Expiry configurable per jurisdiction/cooperative
• Expiry date included in public verifier output

Priority

Low

Estimated Effort

Medium

Dependencies

Certificate detail page

Labels

enhancement, product, compliance

[Dev-Odun-oss]

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

I'd like to work on this issue. I've read through the codebase and I have a clear picture of what needs to be done here. I'll keep the implementation minimal and aligned with the existing patterns in the project.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Dev-Odun-oss to this issue.

[drips-wave]

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

🧑‍💻 @Dev-Odun-oss: 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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