[P1][backend] Add consistent API error response contracts

[dzekojohn4]

Define a documented error schema with request IDs, stable codes, field errors, and safe messages. Ensure global filters and controller exceptions use it consistently.

[DaddyGachi]

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

Hi maintainer, can work on this please? thank you

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[Stanley-Owoh]

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

Good day maintainer please i would like to work on this issue
I can work on this immediately with positive results please assign it to me. Thank you

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[1Psalm]

@1Psalm has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I want to standardize how the backend reports API errors. The core deliverable is a documented error schema with request IDs, stable codes, field errors, and safe messages used consistently by global filters and controller exceptions. My approach is to define the schema once, route all handlers through it, and add tests confirming consistency.

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[339mon]

@339mon has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello maintainer assign this to me Tnx

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[Muyideen-js]

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

Hi, I can fix this

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[drips-wave]

Congratulations, @1Psalm! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @1Psalm: 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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