feat(observability): implement global error handling and standardized…

[shogun444]

Summary

This PR implements standardized global error handling across the backend by introducing consistent error responses, centralized exception mapping, and comprehensive test coverage.

Changes

• Added standardized application error codes (AUTH_001, RES_001, SYS_001, etc.).
• Updated the global exception filter to return a consistent error response format.
• Prevented stack traces from being exposed to API clients while preserving structured server-side logging.
• Registered the global exception filter application-wide.
• Added developer documentation for standardized error codes.
• Updated unit tests and added E2E tests covering standardized responses for 400, 401, 403, 404, 409, 422, 429, 503, and 500.

Verification

• {x} Unit tests passed (6/6).
• {x} E2E tests passed (11/11).
• {x} Error responses now follow the required schema with standardized codes, timestamps, and request IDs.

#Closes #506

[drips-wave]

@shogun444 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[RUKAYAT-CODER]

Nice job. Thank you for contributing to the project