fix(checkout): show backend start errors

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 {
@@ -680,6 +681,34 @@ describe('StoreLayoutComponent', () => {
     expect((fixture.componentInstance as any).isCartOpen()).toBe(false);
   });
 
+  it('shows the backend message when starting checkout fails', async () => {
+    const message = 'Alcanzaste el límite de compra para este producto.';
+    checkoutServiceStub.startCheckout.mockRejectedValue(
+      new HttpErrorResponse({ status: 422, error: { 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);
+    fixture.detectChanges();
+
+    await (fixture.componentInstance as any).onCheckoutClick();
+
+    expect(TestBed.inject(ToastService).danger).toHaveBeenCalledWith(message);
+  });
+
   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 {
@@ -278,7 +279,12 @@ export class StoreLayoutComponent implements OnInit {
       });
     } 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);
+
     } finally {
       this.isCreatingPurchase.set(false);
     }

src/app/features/store/pages/category-items-page/category-items-page.component.ts

@@ -170,7 +170,12 @@ export class CategoryItemsPageComponent {
       await this.router.navigate(['/checkout'], { queryParams: { purchase: purchase.id } });
     } catch (error) {
       console.error('Failed to create direct purchase:', error);
-      this.toastService.danger('No se pudo iniciar la compra directa.');
+      const message =
+        error instanceof HttpErrorResponse && typeof error.error?.message === 'string'
+          ? error.error.message
+          : 'No se pudo iniciar la compra directa.';
+      this.toastService.danger(message);
+
     } finally {
       this.creatingDirectPurchase.set(false);
     }

src/app/features/store/pages/search-page/search-page.component.ts

@@ -202,7 +202,12 @@ export class SearchPageComponent {
       await this.router.navigate(['/checkout'], { queryParams: { purchase: purchase.id } });
     } catch (error) {
       console.error('Failed to create direct purchase:', error);
-      this.toastService.danger('No se pudo iniciar la compra directa.');
+      const message =
+        error instanceof HttpErrorResponse && typeof error.error?.message === 'string'
+          ? error.error.message
+          : 'No se pudo iniciar la compra directa.';
+      this.toastService.danger(message);
+
     } finally {
       this.creatingDirectPurchase.set(false);
     }