fix: add error feedback to PDF/CSV export mutations

Export mutations (annual report PDFs, colony/honey-batch CSV exports)
had no onError handler, so a failed download (network error, expired
session) silently did nothing with zero user feedback. Same silent-
failure class as the earlier onError sweep on entity-save mutations,
here applied to the 5 remaining export/download call sites.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

ApiCore-Frontend/src/app/(app)/apiaries/[id]/page.tsx

@@ -3,6 +3,7 @@
 import Link from "next/link";
 import { useParams } from "next/navigation";
 import { useMutation, useQuery } from "@tanstack/react-query";
+import { toast } from "sonner";
 import { fetchApiary } from "@/lib/apiaries/api";
 import { exportApiaryAnnualReportPdf } from "@/lib/export/api";
 import { QrCodeDialog } from "@/components/qr-code-dialog";
@@ -22,6 +23,7 @@ export default function ApiaryDetailPage() {
 
   const exportReportMutation = useMutation({
     mutationFn: () => exportApiaryAnnualReportPdf(params.id, CURRENT_YEAR),
+    onError: () => toast.error("Jahresbericht konnte nicht exportiert werden"),
   });
 
   if (isLoading) {

ApiCore-Frontend/src/app/(app)/colonies/[id]/page.tsx

@@ -2,6 +2,7 @@
 
 import { useParams } from "next/navigation";
 import { useMutation, useQuery } from "@tanstack/react-query";
+import { toast } from "sonner";
 import { fetchColony } from "@/lib/colonies/api";
 import { exportColonyAnnualReportPdf } from "@/lib/export/api";
 import { QrCodeDialog } from "@/components/qr-code-dialog";
@@ -27,6 +28,7 @@ export default function ColonyDetailPage() {
 
   const exportReportMutation = useMutation({
     mutationFn: () => exportColonyAnnualReportPdf(params.id, CURRENT_YEAR),
+    onError: () => toast.error("Jahresbericht konnte nicht exportiert werden"),
   });
 
   if (isLoading) {

ApiCore-Frontend/src/app/(app)/colonies/page.tsx

@@ -4,6 +4,7 @@ import { useState } from "react";
 import Link from "next/link";
 import { Layers } from "lucide-react";
 import { useMutation, useQuery } from "@tanstack/react-query";
+import { toast } from "sonner";
 import { fetchColonies } from "@/lib/colonies/api";
 import { ColonyStatus } from "@/lib/colonies/types";
 import { COLONY_CONDITION_LABELS, COLONY_STATUS_LABELS, COLONY_TYPE_LABELS } from "@/lib/colonies/labels";
@@ -35,7 +36,10 @@ export default function ColoniesPage() {
     queryFn: () => fetchColonies({}),
   });
 
-  const exportMutation = useMutation({ mutationFn: exportColoniesCsv });
+  const exportMutation = useMutation({
+    mutationFn: exportColoniesCsv,
+    onError: () => toast.error("CSV-Export konnte nicht heruntergeladen werden"),
+  });
 
   const activeColonies = (colonies ?? []).filter((colony) => colony.deactivatedAt === null);
   const historyColonies = (colonies ?? []).filter((colony) => colony.deactivatedAt !== null);

ApiCore-Frontend/src/app/(app)/honey-batches/[id]/page.tsx

@@ -4,6 +4,7 @@ import Link from "next/link";
 import { useParams } from "next/navigation";
 import { Droplet, FlaskConical } from "lucide-react";
 import { useMutation, useQuery } from "@tanstack/react-query";
+import { toast } from "sonner";
 import { fetchHoneyBatch, fetchHoneyBatchTraceability } from "@/lib/honey-batches/api";
 import { HONEY_BATCH_STATUS_LABELS } from "@/lib/honey-batches/labels";
 import { exportHoneyBatchTraceabilityPdf } from "@/lib/export/api";
@@ -32,6 +33,7 @@ export default function HoneyBatchDetailPage() {
 
   const exportPdfMutation = useMutation({
     mutationFn: () => exportHoneyBatchTraceabilityPdf(params.id),
+    onError: () => toast.error("PDF-Bericht konnte nicht exportiert werden"),
   });
 
   if (isLoading) {

ApiCore-Frontend/src/app/(app)/honey-batches/page.tsx

@@ -3,6 +3,7 @@
 import { useState } from "react";
 import { Droplet } from "lucide-react";
 import { useMutation, useQuery } from "@tanstack/react-query";
+import { toast } from "sonner";
 import { fetchHoneyBatches } from "@/lib/honey-batches/api";
 import { HoneyBatchStatus } from "@/lib/honey-batches/types";
 import { HONEY_BATCH_STATUS_LABELS } from "@/lib/honey-batches/labels";
@@ -26,7 +27,10 @@ export default function HoneyBatchesPage() {
     queryFn: () => fetchHoneyBatches({}),
   });
 
-  const exportMutation = useMutation({ mutationFn: exportHoneyBatchesCsv });
+  const exportMutation = useMutation({
+    mutationFn: exportHoneyBatchesCsv,
+    onError: () => toast.error("CSV-Export konnte nicht heruntergeladen werden"),
+  });
 
   const activeBatches = (honeyBatches ?? []).filter(
     (batch) => !HISTORY_STATUSES.includes(batch.status),