Squashed commit of the following:

commit 38d03588b1
Merge: 8e987d0 6f4aa3b
Author: ncoronel <ncoronel@quo.ar>
Date:   Wed Aug 26 10:25:23 2026 -0300

    Merge branch 'fix/cart-expiration-notification' of https://gitea.quo.ar/tbianchini/shopit-front into fix/cart-expiration-notification

commit 8e987d0ce6
Author: ncoronel <ncoronel@quo.ar>
Date:   Wed Aug 26 10:02:26 2026 -0300

    fix(purchase-status): clear cart on approved purchase

commit e171b9a233
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 17:06:07 2026 -0300

    refactor(checkout): use purchase id route segment

commit 643d43adea
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 17:05:59 2026 -0300

    fix(checkout): handle expired purchase exits

commit d89d01b511
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:47:17 2026 -0300

    fix(checkout): refresh expired carts

commit eeb245209b
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:46:12 2026 -0300

    fix(checkout): show backend start errors

commit 9d3754c2d8
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:33:44 2026 -0300

    fix(cart): refresh state after expiration

commit 6f4aa3b1bd
Author: ncoronel <ncoronel@quo.ar>
Date:   Wed Aug 26 10:02:26 2026 -0300

    fix(purchase-status): clear cart on approved purchase

commit 2b342ec235
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 17:06:07 2026 -0300

    refactor(checkout): use purchase id route segment

commit d06b146104
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 17:05:59 2026 -0300

    fix(checkout): handle expired purchase exits

commit f4e0a9e028
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:47:17 2026 -0300

    fix(checkout): refresh expired carts

commit 8c2b738806
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:46:12 2026 -0300

    fix(checkout): show backend start errors

commit 1362d0c163
Author: ncoronel <ncoronel@quo.ar>
Date:   Tue Aug 25 16:33:44 2026 -0300

    fix(cart): refresh state after expiration

src/app/core/guards/menu.guard.spec.ts

@@ -62,7 +62,7 @@ describe('hasMenuGuard', () => {
   });
 
   it('redirects a missing menu route to the store root', () => {
-    const result = runGuard('checkout', '/checkout', tenant);
+    const result = runGuard('checkout', '/checkout/25', tenant);
 
     expect(result instanceof UrlTree).toBe(true);
     expect(TestBed.inject(Router).serializeUrl(result as UrlTree)).toBe('/');

src/app/core/layout/store-layout/store-layout.component.spec.ts

@@ -1,5 +1,6 @@
 import { describe, it, expect, beforeEach, vi } from 'vitest';
 import { signal } from '@angular/core';
+import { HttpErrorResponse } from '@angular/common/http';
 import { TestBed } from '@angular/core/testing';
 import { By } from '@angular/platform-browser';
 import {
@@ -246,7 +247,7 @@ describe('StoreLayoutComponent', () => {
   it('disables the cart icon and prevents opening the popup during checkout with a tenant base path', () => {
     tenantState.set({ ...tenant, base_path: 'fiesta' });
     const router = TestBed.inject(Router);
-    vi.spyOn(router, 'url', 'get').mockReturnValue('/fiesta/checkout?purchase=25');
+    vi.spyOn(router, 'url', 'get').mockReturnValue('/fiesta/checkout/25');
 
     const fixture = TestBed.createComponent(StoreLayoutComponent);
     fixture.detectChanges();
@@ -587,7 +588,7 @@ describe('StoreLayoutComponent', () => {
     const authService = TestBed.inject(AuthService);
     const cartService = TestBed.inject(CartService);
     const router = TestBed.inject(Router);
-    vi.spyOn(router, 'url', 'get').mockReturnValue('/checkout?purchase=25');
+    vi.spyOn(router, 'url', 'get').mockReturnValue('/checkout/25');
     const navigateSpy = vi.spyOn(router, 'navigate').mockResolvedValue(true);
 
     const fixture = TestBed.createComponent(StoreLayoutComponent);
@@ -674,12 +675,44 @@ describe('StoreLayoutComponent', () => {
     expect(checkoutServiceStub.startCheckout).toHaveBeenCalledWith('test', {
       cart_id: 1,
     });
-    expect(router.navigate).toHaveBeenCalledWith(['/checkout'], {
-      queryParams: { purchase: 55 },
-    });
+    expect(router.navigate).toHaveBeenCalledWith(['/checkout', 55]);
     expect((fixture.componentInstance as any).isCartOpen()).toBe(false);
   });
 
+  it('shows the backend message and refreshes the cart when its reservation expired', async () => {
+    const message = 'La reserva de stock venció. Usá el carrito activo para continuar.';
+    checkoutServiceStub.startCheckout.mockRejectedValue(
+      new HttpErrorResponse({
+        status: 422,
+        error: { code: 'stock_reservation.expired', message },
+      }),
+    );
+    cartState.set({
+      id: 1,
+      tenant_codigo: tenant.codigo,
+      status: 'active',
+      subtotal: '100.00',
+      items: [],
+    });
+    authUserState.set({
+      id: 7,
+      nombre_apellido: 'Juan Perez',
+      email: 'juan@example.com',
+      dni: '12345678',
+      telefono: '3415555555',
+    });
+
+    const fixture = TestBed.createComponent(StoreLayoutComponent);
+    const loadCart = vi.spyOn(TestBed.inject(CartService), 'loadCart');
+    fixture.detectChanges();
+    loadCart.mockClear();
+
+    await (fixture.componentInstance as any).onCheckoutClick();
+
+    expect(TestBed.inject(ToastService).danger).toHaveBeenCalledWith(message);
+    expect(loadCart).toHaveBeenCalledOnce();
+  });
+
   it('allows modifying quantities directly in the regular cart without a toggle', () => {
     cartState.set({
       id: 1,

src/app/core/layout/store-layout/store-layout.component.ts

@@ -1,3 +1,4 @@
+import { HttpErrorResponse } from '@angular/common/http';
 import { Component, computed, DestroyRef, inject, OnInit, signal } from '@angular/core';
 import { takeUntilDestroyed } from '@angular/core/rxjs-interop';
 import {
@@ -17,7 +18,10 @@ import { ButtonComponent } from '../../../shared/components/button/button.compon
 import { CartItem, CartItemVariantValue } from '../../services/cart/cart.interface';
 import { AuthService } from '../../services/auth/auth.service';
 import { findMenu } from '../../services/menu.utils';
-import { CheckoutService } from '../../services/checkout.service';
+import {
+  CheckoutService,
+  isExpiredStockReservationResponse,
+} from '../../services/checkout.service';
 import { ToastService } from '../../services/toast.service';
 import { Category } from '../../services/tenant.interface';
 
@@ -273,12 +277,20 @@ export class StoreLayoutComponent implements OnInit {
       });
 
       this.isCartOpen.set(false);
-      await this.router.navigate(['/checkout'], {
-        queryParams: { purchase: purchase.id },
-      });
+      await this.router.navigate(['/checkout', purchase.id]);
     } catch (error) {
       console.error('Failed to create cart purchase:', error);
-      this.toastService.danger('No se pudo iniciar la compra.');
+      const message =
+        error instanceof HttpErrorResponse && typeof error.error?.message === 'string'
+          ? error.error.message
+          : 'No se pudo iniciar la compra.';
+      this.toastService.danger(message);
+
+      if (error instanceof HttpErrorResponse && isExpiredStockReservationResponse(error.error)) {
+        this.cartService.loadCart().subscribe({
+          error: (refreshError) => console.error('Error refreshing expired cart', refreshError),
+        });
+      }
     } finally {
       this.isCreatingPurchase.set(false);
     }

src/app/core/services/auth/auth.guards.spec.ts

@@ -24,12 +24,12 @@ describe('auth guards', () => {
     });
 
     const result = TestBed.runInInjectionContext(() =>
-      authGuard(null as never, { url: '/checkout?mode=direct' } as never),
+      authGuard(null as never, { url: '/checkout/25' } as never),
     );
 
     expect(result instanceof UrlTree).toBe(true);
     expect(TestBed.inject(Router).serializeUrl(result as UrlTree)).toBe(
-      '/login?returnUrl=%2Fcheckout%3Fmode%3Ddirect',
+      '/login?returnUrl=%2Fcheckout%2F25',
     );
   });
 
@@ -39,7 +39,7 @@ describe('auth guards', () => {
     });
 
     const result = TestBed.runInInjectionContext(() =>
-      authGuard(null as never, { url: '/checkout' } as never),
+      authGuard(null as never, { url: '/checkout/25' } as never),
     );
 
     expect(result).toBe(true);

src/app/core/services/checkout.service.ts

@@ -45,6 +45,21 @@ export function isInsufficientStockResponse(value: unknown): value is Insufficie
   );
 }
 
+export interface ExpiredStockReservationResponse {
+  code: 'stock_reservation.expired';
+  message: string;
+}
+
+export function isExpiredStockReservationResponse(
+  value: unknown,
+): value is ExpiredStockReservationResponse {
+  return (
+    typeof value === 'object' &&
+    value !== null &&
+    (value as Partial<ExpiredStockReservationResponse>).code === 'stock_reservation.expired'
+  );
+}
+
 export type StartCheckoutPayload =
   | {
       cart_id: number;