refactor(auth): fix checkOAuthUserProfile error propagation (avoid writing to res)

[PierreBrisorgueil]

Context

Raised by Copilot review on #3134.

Problem

checkOAuthUserProfile() in modules/auth/controllers/auth.controller.js writes directly to res on validation failure and returns the response object:

if (error) return responses.error(res, 422, 'Schema validation error', error)(result.error);

The caller oauthCallback() then treats the returned value as a user and proceeds to sign a JWT and set cookies — leading to a potential double response (ERR_HTTP_HEADERS_SENT) and an incorrect auth flow.

Fix

checkOAuthUserProfile should throw an error (e.g. AppError) on validation failure instead of writing to res. oauthCallback already wraps the call in a try/catch, so the thrown error would be caught and handled cleanly by the existing responses.error(res, 422, ...) path.

// Instead of writing to res:
if (error) throw new AppError('Schema validation error', { code: 'VALIDATION_ERROR', details: error });