Update auth Zod schemas for device payloads

[codebestia]

Extend apps/backend/src/schemas/auth.schemas.ts VerifySchema with a nested device object schema. Validate deviceId as UUID, platform in enum, identityPublicKey as base64 of expected length, deviceName length-bounded. Export the device sub-schema for reuse by POST /devices.

Acceptance criteria:

• Verify rejects malformed device payloads with field-level errors
• Device sub-schema reused by /devices route

[Jaydams]

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

I would love to be assigned this issue.

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[Agbeleshe]

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

Hey, can I solve this? I intend to understand the current code flow first, then develop a clean and scalable implementation that adheres to the project's conventions. I'll also verify the implementation with appropriate tests before submitting my work.

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[drips-wave]

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

🧑‍💻 @Agbeleshe: 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.

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