fix(planner): a create expense click that saves nothing no longer opens the editor on the next save

In the desktop booking and transport dialogs, clicking "Create expense"
(or editing a linked expense) before the booking had a title saved
nothing, which is right, but the wish was kept. The next ordinary save
then opened the expense editor out of nowhere. The same happened after a
save that threw.

useBookingExpenseIntent stored the wish in a ref and only cleared it when
the form read it, which the desktop forms do after a successful save. The
hook now clears the wish once the save its click started has settled,
unless a newer click replaced it in the meantime. The phone sheets read
it at the start of the save and are unaffected.

Red tests:
- FE-PLANNER-RESMODAL-107 in ReservationModal.test.tsx: "expected
  "vi.fn()" to not be called at all, but actually been called 1 times".
- FE-PLANNER-BOOKINGEXPENSE-005 in useBookingExpenseIntent.test.ts:
  "expected { create: true } to be null".
- FE-PLANNER-BOOKINGEXPENSE-006: "expected { editItem: { id: 9, ... } }
  to be null".

No existing assertions changed.

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

@@ -1,4 +1,4 @@
-// FE-PLANNER-RESMODAL-001 to FE-PLANNER-RESMODAL-106
+// FE-PLANNER-RESMODAL-001 to FE-PLANNER-RESMODAL-107
 import { render, screen, waitFor, fireEvent, within, act } from '../../../tests/helpers/render';
 import userEvent from '@testing-library/user-event';
 import { http, HttpResponse } from 'msw';
@@ -1441,6 +1441,22 @@ describe('ReservationModal', () => {
     );
   });
 
+  it('FE-PLANNER-RESMODAL-107: a create-expense click that saves nothing does not open the editor on the next plain save', async () => {
+    budgetEnabled();
+    const onSave = vi.fn().mockResolvedValue({ id: 85 });
+    const onOpenExpense = vi.fn();
+    render(<ReservationModal {...defaultProps} onSave={onSave} onOpenExpense={onOpenExpense} />);
+
+    // No title yet: the save returns early and nothing is created.
+    await userEvent.click(screen.getByRole('button', { name: /Create expense/i }));
+    expect(onSave).not.toHaveBeenCalled();
+
+    await userEvent.type(screen.getByPlaceholderText(/e\.g\. Lufthansa/i), 'Dinner');
+    await userEvent.click(screen.getByRole('button', { name: /^Add$/i }));
+    await waitFor(() => expect(onSave).toHaveBeenCalledTimes(1));
+    expect(onOpenExpense).not.toHaveBeenCalled();
+  });
+
   // ── File error paths ────────────────────────────────────────────────────────
 
   it('FE-PLANNER-RESMODAL-077: a cancelled file dialog changes nothing', () => {

client/src/components/Planner/useBookingExpenseIntent.test.ts

@@ -1,4 +1,4 @@
-// FE-PLANNER-BOOKINGEXPENSE-001 to -004: the expense wish of the booking and
+// FE-PLANNER-BOOKINGEXPENSE-001 to -006: the expense wish of the booking and
 // transport forms, desktop and phone alike.
 import { act, renderHook } from '@testing-library/react';
 import { describe, expect, it, vi } from 'vitest';
@@ -51,4 +51,33 @@ describe('useBookingExpenseIntent', () => {
     await expect(result.current.remove(buildBudgetItem())).resolves.toBeUndefined();
     expect(submit).not.toHaveBeenCalled();
   });
+
+  it('FE-PLANNER-BOOKINGEXPENSE-005: a save that ends without reading the wish does not leave it for the next save', async () => {
+    // The desktop reads the wish only after a successful save; an empty title
+    // returns before that point.
+    const submit = vi.fn(async () => undefined);
+    const { result } = renderHook(() => useBookingExpenseIntent(submit));
+    await act(async () => result.current.create());
+    expect(result.current.take()).toBeNull();
+  });
+
+  it('FE-PLANNER-BOOKINGEXPENSE-006: a save that throws does not leave the wish for the next save', async () => {
+    let fail: (e: Error) => void = () => undefined;
+    const submit = vi.fn(
+      () =>
+        new Promise<void>((_resolve, reject) => {
+          fail = reject;
+        })
+    );
+    const unhandled = vi.fn();
+    process.on('unhandledRejection', unhandled);
+    try {
+      const { result } = renderHook(() => useBookingExpenseIntent(submit));
+      act(() => result.current.edit(buildBudgetItem({ id: 9 })));
+      await act(async () => fail(new Error('save failed')));
+      expect(result.current.take()).toBeNull();
+    } finally {
+      process.off('unhandledRejection', unhandled);
+    }
+  });
 });

client/src/components/Planner/useBookingExpenseIntent.ts

@@ -20,6 +20,16 @@ export interface BookingExpenseRemoval {
 export function useBookingExpenseIntent(submit: () => Promise<unknown>, removal?: BookingExpenseRemoval) {
   const intentRef = useRef<BookingExpenseIntent | null>(null);
 
+  // The wish belongs to the save its click starts. A save that returns early
+  // (no title) or throws never reads it, and it must not open the editor on
+  // the next, unrelated save. A newer click's wish is left alone.
+  const saveWith = (intent: BookingExpenseIntent) => {
+    intentRef.current = intent;
+    void submit().finally(() => {
+      if (intentRef.current === intent) intentRef.current = null;
+    });
+  };
+
   return {
     /** Forgets a wish left from an earlier opening. */
     reset: () => {
@@ -31,15 +41,9 @@ export function useBookingExpenseIntent(submit: () => Promise<unknown>, removal?
       intentRef.current = null;
       return intent;
     },
-    create: () => {
-      intentRef.current = { create: true };
-      void submit();
-    },
+    create: () => saveWith({ create: true }),
     /** Saves the booking first, then opens the linked expense. */
-    edit: (item: BudgetItem) => {
-      intentRef.current = { editItem: item };
-      void submit();
-    },
+    edit: (item: BudgetItem) => saveWith({ editItem: item }),
     remove: async (item: BudgetItem) => {
       if (!removal) return;
       try {