IS-11347 Unify completed-with-success and completed-with-error handling

[aleixsuau]

Jira: https://curity.atlassian.net/browse/IS-11347

Summary

Unifies completed-with-success and completed-with-error HAAPI step handling under a single handleCompletedStep with one config knob — autoRedirectOnAuthenticationComplete. Previously the LWA auto-redirected on success but exposed errors as nextStepData, even though both server-side step shapes carry an authorization-response link and the Velocity-rendered UI auto-redirects in both cases.

Config

autoRedirectOnAuthenticationComplete: boolean | AUTO_REDIRECT_ON_AUTHENTICATION_COMPLETE (default true).

• true → redirect on both success and error
• false → expose the completed step as nextStepData for both
• 'ONLY_ON_SUCCESS' → redirect on success, expose on error
• 'ONLY_ON_ERROR' → redirect on error, expose on success

Breaking rename of redirectOnAuthenticationCompletedWithSuccess — safe because the LWA is still pre-1.0 and has no external consumers.

Test plan

• CI green (tsc, eslint, vitest, prettier)
• Manually verify: HAAPI flow ending in completed-with-error (e.g. unknown client_id) auto-redirects under default config
• Manually verify: autoRedirectOnAuthenticationComplete: 'ONLY_ON_SUCCESS' causes the error step to surface as nextStepData
• Manually verify: existing success flow still redirects (no regression)