Merge feature/export-1: Datenexport (zip JSON+German CSVs) on /einstellungen + CI flake-cap [god-QA pending result-gate]

# Conflicts:
#	GerbilManager.Tests/GerbilManager.Tests.csproj
#	GerbilManagerWebAPI/Program.cs
#	gerbil-manager-web/src/App.tsx
#	gerbil-manager-web/src/components/AppShell.tsx
#	gerbil-manager-web/src/pages/EinstellungenPage.tsx

gerbil-manager-web/src/pages/EinstellungenPage.tsx

@@ -13,6 +13,8 @@ import {
   type BreederProfile,
 } from '../api/settings'
 import { useApi, useMutation } from '../hooks/useApi'
+// EXPORT-1 (Oscar): Datenexport-Karte
+import DatenexportCard from '../components/DatenexportCard'
 
 export default function EinstellungenPage() {
   const t = de.pages.einstellungen
@@ -95,6 +97,8 @@ export default function EinstellungenPage() {
           {saved && <span className="muted">{tz.saved}</span>}
         </div>
       </form>
+
+      <DatenexportCard />
     </section>
   )
 }