Validate OAuth state parameter on Discord login callback

[RUKAYAT-CODER]

Background

The Discord OAuth callback does not verify the state nonce, allowing login CSRF. Generate and validate a state value.

Files to modify (2-3)

src/lib/discord/oauth.ts
src/middleware/security.ts

Acceptance Criteria

Implemented across the listed files

Unit/integration tests added or updated and passing

No regression; follows project coding standards

[DavisVT]

@DavisVT has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

i'm a developer well fit for implementing this task
Kindly assign them to me

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

[drips-wave]

Congratulations, @DavisVT! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @DavisVT: 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.

🌊 Happy Wave 🌊

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox!

@DavisVT's PR #1317 was approved and merged by @RUKAYAT-CODER.

🏆 @DavisVT: You earned 40 FoxPoints for this contribution! Your current tier: Builder (2,147 total points). Track your full progress on GrantFox.

👏 Great work, @DavisVT! Keep contributing to rinafcode.