test(import): read the upload body instead of parsing it as FormData

These are the only two test files that call request.formData() inside an MSW
handler, and they hold exactly the three tests that failed on CI while passing
locally. The body axios' XHR adapter produces under jsdom is one Node 24's
multipart parser rejects, so the handler threw before reading a field and the
component reported a failed upload. Reading the raw payload asserts the same
thing without depending on the parser.

client/src/components/Planner/BookingImportModal.test.tsx

@@ -3,6 +3,7 @@ import { render, screen, fireEvent, waitFor } from '../../../tests/helpers/rende
 import userEvent from '@testing-library/user-event';
 import { http, HttpResponse } from 'msw';
 import { server } from '../../../tests/helpers/msw/server';
+import { readMultipart } from '../../../tests/helpers/multipart';
 import { useBackgroundTasksStore } from '../../store/backgroundTasksStore';
 import { resetAllStores } from '../../../tests/helpers/store';
 import { saveImportFiles } from '../../db/offlineDb';
@@ -111,8 +112,7 @@ describe('BookingImportModal', () => {
     let sentMode: string | null = null;
     server.use(
       http.post('/api/trips/4/reservations/import/booking/async', async ({ request }) => {
-        const fd = await request.formData();
-        sentMode = String(fd.get('mode'));
+        sentMode = (await readMultipart(request)).fields.mode ?? null;
         return HttpResponse.json({ jobId: 'job-42' });
       }),
     );
@@ -132,8 +132,7 @@ describe('BookingImportModal', () => {
     server.use(
       http.get('/api/health/features', () => HttpResponse.json({ bookingImport: true, aiParsing: true })),
       http.post('/api/trips/4/reservations/import/booking/async', async ({ request }) => {
-        const fd = await request.formData();
-        sentMode = String(fd.get('mode'));
+        sentMode = (await readMultipart(request)).fields.mode ?? null;
         return HttpResponse.json({ jobId: 'job-ai' });
       }),
     );

client/src/components/Planner/FileImportModal.test.tsx

@@ -2,6 +2,7 @@
 import { render, screen, fireEvent, waitFor } from '../../../tests/helpers/render';
 import { http, HttpResponse } from 'msw';
 import { server } from '../../../tests/helpers/msw/server';
+import { readMultipart } from '../../../tests/helpers/multipart';
 import { useTripStore } from '../../store/tripStore';
 import { resetAllStores, seedStore } from '../../../tests/helpers/store';
 import { buildTrip } from '../../../tests/helpers/factories';
@@ -127,11 +128,11 @@ describe('FileImportModal', () => {
     let flags: Record<string, string> = {};
     server.use(
       http.post('/api/trips/3/places/import/gpx', async ({ request }) => {
-        const fd = await request.formData();
+        const { fields } = await readMultipart(request);
         flags = {
-          waypoints: String(fd.get('importWaypoints')),
-          routes: String(fd.get('importRoutes')),
-          tracks: String(fd.get('importTracks')),
+          waypoints: fields.importWaypoints,
+          routes: fields.importRoutes,
+          tracks: fields.importTracks,
         };
         return HttpResponse.json({ count: 4, skipped: 0, places: [{ id: 11 }, { id: 12 }] });
       }),