HELP-1: in-app German user guide (/hilfe, accordion, 9 sections)

HilfePage.tsx: accordion via <details>/<summary> (native, accessible, mobile-first);
9 sections in du-Form: Erste Schritte, Rennmaeuse, Becken, Wuerfe, Genetik,
Stammbaum, Abgabe-Ablauf, Statistik, Datensicherung. All UI labels imported from
de.ts (rename-safe); SCHECKE/Rex warnings verbatim from genetics.warnings.

de.ts: de.nav.help + de.hilfe (title, subtitle, 9 section keys)
AppShell.tsx: Hilfe (heart question mark) added to SECONDARY nav (Mehr-sheet on phone,
sidebar on desktop)
App.tsx: Route path=hilfe -> <HilfePage />
hilfe.css: accordion, hint boxes, warning colour; piggybacks on existing CSS vars

e2e/hilfe.spec.ts: 3 smoke tests x 2 viewports = 6 new tests
  -- Hilfe reachable via nav
  -- First accordion section expands on click
  -- SCHECKE warning visible in Genetik section

Full evidence: dotnet test 18/18, npm test 47/47, npm run build ok,
npm run e2e 54/54 (48 existing + 6 new hilfe tests).

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

gerbil-manager-web/src/components/AppShell.tsx

@@ -23,6 +23,7 @@ const SECONDARY: NavItem[] = [
   { to: '/kontakte', label: de.nav.contacts, icon: '📇' },
   { to: '/abgabe', label: de.nav.forSale, icon: '🏡' },
   { to: '/statistik', label: de.nav.statistics, icon: '📊' },
+  { to: '/hilfe', label: de.nav.help, icon: '❓' },
 ]
 
 const linkClass = ({ isActive }: { isActive: boolean }) =>