[Chore] Add .github/CODEOWNERS for review routing

[grantfox-oss]

Telegram (ask questions / claim the issue here first): https://t.me/+DOylgFv1jyJlNzM0

Why this matters

There is no CODEOWNERS file anywhere in the repo (.github/ has ISSUE_TEMPLATE, workflows, dependabot.yml, pull_request_template.md, codecov.yml but no CODEOWNERS), so PRs touching backend/, frontend/, or contracts/ have no auto-assigned reviewers in this monorepo.

Acceptance criteria

• Add .github/CODEOWNERS mapping backend/, frontend/, contracts/, docs/, and .github/ to appropriate maintainers
• Confirm GitHub recognizes the file (no parse errors in the Code owners UI)

Files to touch

• .github/CODEOWNERS

Out of scope

• Configuring branch protection / required reviews

[Windowlight]

@Windowlight has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I’m interested in this issue and believe my experience with contracts, backend systems, and frontend implementation makes me a good fit. Happy to provide updates as I work through it.

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

[dinahmaccodes]

@dinahmaccodes has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello maintainer, my name is Dinah and I am a solid developer.
I can work on this and solve the problem easily.
Can I be assigned this issue??

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

[grantfox-oss]

🦊 GrantFox — @dinahmaccodes has been assigned to this issue!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #904)
2. Your PR will be reviewed by the LabsCrypt maintainers

Good luck! Track your progress on GrantFox.

[drips-wave]

Congratulations, @dinahmaccodes! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @dinahmaccodes: 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 🌊