Fails fast before the API call with a clear German error message.
Tests boundary: 100 chars accepted, 101 rejected.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Creates household via POST /v1/households, redirects to /household/staples.
Load guard redirects users who already have a household to /planner.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>