Standardize API validation error format across all endpoints

[nanaf6203-bit]

Problem

ValidationPipe errors format may be inconsistent: field names in camelCase vs snake_case, nested errors structure varies, no error codes.

Expected Outcome

Standardized validation error format with error codes and consistent field naming.

Acceptance Criteria

• Consistent error format: { field, message, code, constraints }
• Field names follow API convention (camelCase)
• Error codes for each validation type
• Documentation of error format

Files Affected

src/common/filters/validation-exception.filter.ts (new)

Difficulty

Easy

Estimated Effort

Small (1 day)

Labels

api, enhancement, developer-experience

[Moonwalker-rgb]

@Moonwalker-rgb has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hi maintainer
i would love to be assigned this issue to fix

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

[drips-wave]

Congratulations, @Moonwalker-rgb! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @Moonwalker-rgb: 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 🌊