feat(frontend): Export-Buttons fuer Voelker, Honigchargen (Modul 21)

CSV-Export in den Listen-Views (Voelker, Honigchargen) und
PDF-Rueckverfolgbarkeitsbericht auf der Honigcharge-Detailseite.
apiFetchBlob() im API-Client ergaenzt fuer authentifizierte
Blob-Downloads (JWT im Authorization-Header statt Cookie).

ApiCore-Frontend/src/lib/auth/api-client.ts

@@ -25,6 +25,39 @@ async function rawFetch(path: string, init: RequestInit): Promise<Response> {
   });
 }
 
+export interface BlobDownload {
+  blob: Blob;
+  filename: string;
+}
+
+function filenameFromContentDisposition(header: string | null, fallback: string): string {
+  const match = header ? /filename="([^"]+)"/.exec(header) : null;
+  return match?.[1] ?? fallback;
+}
+
+export async function apiFetchBlob(path: string, fallbackFilename: string): Promise<BlobDownload> {
+  let response = await rawFetch(path, {});
+
+  if (response.status === 401) {
+    const refreshed = await refreshRequest();
+    if (refreshed) {
+      setAccessToken(refreshed.accessToken);
+      response = await rawFetch(path, {});
+    }
+  }
+
+  if (!response.ok) {
+    throw new ApiError(response.status, 'Export fehlgeschlagen');
+  }
+
+  const blob = await response.blob();
+  const filename = filenameFromContentDisposition(
+    response.headers.get('Content-Disposition'),
+    fallbackFilename,
+  );
+  return { blob, filename };
+}
+
 export async function apiFetch<T>(path: string, init: RequestInit = {}): Promise<T> {
   let response = await rawFetch(path, init);