[BUG] Onboarding data-handling 'Weiter' button kaputt (System Import fehlt)

[Delqhi]

Symptom

Auf /onboarding/data-handling reagiert der 'Weiter'-Button nicht. User bleibt auf der letzten Onboarding-Step hängen.

Root Cause

frontend/src/pages/OnboardingFlow/Steps/DataHandling/index.jsx ruft System.markOnboardingComplete() auf aber System war nirgends importiert. ReferenceError beim Click → silent crash → nichts passiert.

Fix

Commit a6cd3b9a: Import System from '@/models/system' ergänzt.
Zusätzlich f775b91d: useCallback für forward/back handlers gegen stale-closure Bug.

Verifiziert

• Playwright-Test: Click → URL wird / (Home) → DB onboarding_complete=true
• Container muss restartet werden nach docker cp dist/

Lessons

• ESLint-Regel für unused imports hat den Bug nicht gefangen weil System global verfügbar wirkt
• Test-Pattern: jeden @agent / forward-Button mit Playwright klicken + URL-Change verifizieren

[Delqhi]

✅ ALREADY FIXED in commit 8a03fc7 (prior to this session)

What was broken:
Onboarding flow's DataHandling step had a broken "Weiter" (Continue) button because:

1. System model was never imported: import System from "@/models/system"; was missing
2. handleForward called System.markOnboardingComplete() which threw ReferenceError: System is not defined
3. The error was silent (not caught), so the button appeared to do nothing

Fix applied (8a03fc7):
import System from "@/models/system"; // Added missing import

Also wrapped handlers in useCallback for stable references and fixed useEffect dependencies.

Regression test added: tests/index.test.jsx verifies:

• Import exists statically
• Mocked System.markOnboardingComplete is called on button click
• Navigation to home occurs after completion

Verification: All 4 DataHandling tests pass; ESLint passes; production build succeeds.

[Delqhi]

Fixed in commit 8a03fc7 and included in the deployed v0.56.3 image.\n\nVerified today:\n- The System import is present in DataHandling/index.jsx and the Weiter button uses useCallback.\n- The 4 DataHandling regression tests (issue #101/#113) pass.\n- The backend onboarding auth gate was also hardened so POST /onboarding works without auth while onboarding is incomplete, and requires auth once onboarding is complete.\n\nClosing as resolved.