feat: add time zone support for rent payment and refund processes

- Updated API requests and responses to include time zone information.
- Modified backend services to handle time zone for received and refunded dates.
- Adjusted frontend components to use local date formatting based on the user's time zone.
- Enhanced tests to validate time zone handling in rent payment and refund scenarios.

frontend/src/app/components/rent-payment-dialogs.spec.ts

@@ -8,7 +8,7 @@ import { RentPaymentRefundDialog } from './rent-payment-refund-dialog/rent-payme
 import { RentPaymentReversalDialog } from './rent-payment-reversal-dialog/rent-payment-reversal-dialog';
 import { RentPaymentValidationDialog } from './rent-payment-validation-dialog/rent-payment-validation-dialog';
 import { RentDue } from '../services/lease.service';
-import { utcIsoDate } from '../services/rent-payment-format';
+import { browserTimeZone, localIsoDate } from '../services/rent-payment-format';
 import { RentPayment, RentPaymentService } from '../services/rent-payment.service';
 
 describe('rent payment dialogs', () => {
@@ -24,8 +24,10 @@ describe('rent payment dialogs', () => {
     vi.clearAllMocks();
   });
 
-  it('uses UTC for payment and refund date defaults', () => {
-    expect(utcIsoDate(new Date('2026-07-18T23:30:00Z'))).toBe('2026-07-18');
+  it('uses the user local date for payment and refund defaults', () => {
+    const instant = new Date('2026-07-19T06:30:00Z');
+    expect(localIsoDate(instant, 'America/Los_Angeles')).toBe('2026-07-18');
+    expect(localIsoDate(instant, 'Europe/Paris')).toBe('2026-07-19');
   });
 
   it('records one received amount and exposes its surplus outcome', () => {
@@ -44,6 +46,7 @@ describe('rent payment dialogs', () => {
       operationId: expect.any(String),
       rentDueId: 'due-1',
       rentDueVersion: 2,
+      timeZone: browserTimeZone,
       receivedAt: component.today,
       amount: 950,
     });
@@ -102,7 +105,7 @@ describe('rent payment dialogs', () => {
     component.submit();
     expect(payments.refund).toHaveBeenCalledWith(
       'payment-1',
-      expect.objectContaining({ amount: 100, paymentVersion: 3 }),
+      expect.objectContaining({ amount: 100, paymentVersion: 3, timeZone: browserTimeZone }),
     );
   });
 

frontend/src/app/components/rent-payment-refund-dialog/rent-payment-refund-dialog.ts

@@ -14,7 +14,7 @@ import { MatInputModule } from '@angular/material/input';
 import { MatProgressSpinnerModule } from '@angular/material/progress-spinner';
 import { finalize } from 'rxjs';
 import { httpErrorMessage } from '../../services/http-error-message';
-import { formatEuro, utcIsoDate } from '../../services/rent-payment-format';
+import { browserTimeZone, formatEuro, localIsoDate } from '../../services/rent-payment-format';
 import { RentPayment, RentPaymentService } from '../../services/rent-payment.service';
 import { isRentPaymentDataStale, RENT_PAYMENT_DATA_STALE } from '../rent-payment-dialog-result';
 
@@ -36,7 +36,7 @@ export class RentPaymentRefundDialog {
   private readonly dialogRef = inject(MatDialogRef<RentPaymentRefundDialog>);
   private readonly payments = inject(RentPaymentService);
   private readonly operationId = crypto.randomUUID();
-  readonly today = utcIsoDate();
+  readonly today = localIsoDate();
   readonly saving = signal(false);
   readonly error = signal('');
   readonly formatEuro = formatEuro;
@@ -65,6 +65,7 @@ export class RentPaymentRefundDialog {
       .refund(this.payment.id, {
         operationId: this.operationId,
         paymentVersion: this.payment.version,
+        timeZone: browserTimeZone,
         ...this.form.getRawValue(),
       })
       .pipe(finalize(() => this.saving.set(false)))

frontend/src/app/components/rent-payment-validation-dialog/rent-payment-validation-dialog.ts

@@ -16,7 +16,7 @@ import { toSignal } from '@angular/core/rxjs-interop';
 import { finalize } from 'rxjs';
 import { RentDue } from '../../services/lease.service';
 import { httpErrorMessage } from '../../services/http-error-message';
-import { formatEuro, utcIsoDate } from '../../services/rent-payment-format';
+import { browserTimeZone, formatEuro, localIsoDate } from '../../services/rent-payment-format';
 import { RentPaymentService } from '../../services/rent-payment.service';
 import { isRentPaymentDataStale, RENT_PAYMENT_DATA_STALE } from '../rent-payment-dialog-result';
 
@@ -43,7 +43,7 @@ export class RentPaymentValidationDialog {
   private readonly dialogRef = inject(MatDialogRef<RentPaymentValidationDialog>);
   private readonly payments = inject(RentPaymentService);
   private readonly operationId = crypto.randomUUID();
-  readonly today = utcIsoDate();
+  readonly today = localIsoDate();
   readonly saving = signal(false);
   readonly error = signal('');
   readonly formatEuro = formatEuro;
@@ -82,6 +82,7 @@ export class RentPaymentValidationDialog {
         operationId: this.operationId,
         rentDueId: this.data.rentDue.id,
         rentDueVersion: this.data.rentDue.version,
+        timeZone: browserTimeZone,
         ...this.form.getRawValue(),
       })
       .pipe(finalize(() => this.saving.set(false)))

frontend/src/app/services/rent-payment-format.ts

@@ -9,6 +9,8 @@ export function formatEuro(value: number): string {
   return euroFormatter.format(value);
 }
 
-export function utcIsoDate(date = new Date()): string {
-  return date.toISOString().slice(0, 10);
+export const browserTimeZone = Intl.DateTimeFormat().resolvedOptions().timeZone;
+
+export function localIsoDate(date = new Date(), timeZone = browserTimeZone): string {
+  return new Intl.DateTimeFormat('sv-SE', { timeZone }).format(date);
 }

frontend/src/app/services/rent-payment.service.spec.ts

@@ -19,6 +19,7 @@ describe('RentPaymentService', () => {
       rentDueVersion: 2,
       receivedAt: '2026-01-05',
       amount: 900,
+      timeZone: 'America/Los_Angeles',
     };
     const allocation = {
       operationId: 'operation-2',
@@ -32,6 +33,7 @@ describe('RentPaymentService', () => {
       paymentVersion: 2,
       amount: 25,
       refundedAt: '2026-01-06',
+      timeZone: 'America/Los_Angeles',
     };
 
     service.getRentPayments().subscribe();

frontend/src/app/services/rent-payment.service.ts

@@ -47,6 +47,7 @@ export interface RecordRentPaymentRequest {
   rentDueVersion: number;
   receivedAt: string;
   amount: number;
+  timeZone: string;
 }
 
 export interface AllocateRentPaymentRequest {
@@ -62,6 +63,7 @@ export interface RefundRentPaymentRequest {
   paymentVersion: number;
   amount: number;
   refundedAt: string;
+  timeZone: string;
 }
 
 @Injectable({ providedIn: 'root' })