DocumentViewer: loading / error / no-scan / image rendering branches.
filePath conditionally drives the direct-download link in the error
state; fileUrl + non-PDF contentType drives the <img> render.
PersonalInfoForm: default render, prop hydration including the German
date conversion path, success/error banner branches, form action wiring.
profile/+page: notification-checkbox enabled/disabled depending on
hasEmail, no-email hint visibility, prefsSuccess/prefsError banners,
fallback when notificationPrefs is null.
20 tests across three files.
Refs #496.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
