feat: enhance checkout process with purchase editing and status handling

- Implemented purchase editing functionality in CheckoutPageComponent, allowing users to modify items in their purchase.
- Added a new guard (checkoutPendingPurchaseGuard) to prevent navigation away from the checkout page while a purchase is in progress.
- Updated the login page to handle return URLs after authentication.
- Enhanced product detail page to support direct purchases with a new buyNow method.
- Introduced new UI elements and logic to handle purchase status, including expired and rejected states in PurchaseStatusPageComponent.
- Improved cart component to allow editing of item quantities with a toggle button.
- Added quantity selector enhancements to disable controls when necessary.
- Updated tests to cover new functionalities and ensure proper behavior of components.

src/app/shared/components/cart/cart.component.ts

@@ -4,6 +4,7 @@ import {
   computed,
   inject,
   input,
+  model,
   output,
   signal,
 } from '@angular/core';
@@ -48,11 +49,21 @@ export class CartComponent {
   readonly discount = input<number>(0);
   readonly total = input<number>(0);
   readonly backgroundColor = input<string>('#ffffff');
+  readonly readonly = input<boolean>(false);
+  readonly allowEditing = input<boolean>(false);
+  readonly allowRemove = input<boolean>(true);
+  readonly persistQuantityChanges = input<boolean>(true);
+  readonly editingDisabled = input<boolean>(false);
+  readonly editing = model<boolean>(false);
 
   readonly closed = output<void>();
+  readonly itemQuantityChange = output<{
+    item: CartItemMock;
+    index: number;
+    quantity: number;
+  }>();
 
   protected readonly quantityOverrides = signal<Record<number, number>>({});
-
   constructor() {
     this.quantityUpdates$
       .pipe(
@@ -103,6 +114,20 @@ export class CartComponent {
 
   protected onItemQuantityChange(index: number, newQuantity: number): void {
     const mockItem = this.items()[index];
+    if (!mockItem) {
+      return;
+    }
+
+    this.itemQuantityChange.emit({
+      item: mockItem,
+      index,
+      quantity: newQuantity,
+    });
+
+    if (!this.persistQuantityChanges()) {
+      return;
+    }
+
     const cartItemId = mockItem?.cartItemId;
     if (cartItemId) {
       this.quantityOverrides.update((overrides) => ({
@@ -153,6 +178,15 @@ export class CartComponent {
   protected readonly formattedDiscount = computed(() => this.formatCurrency(this.discount()));
   protected readonly formattedTotal = computed(() => this.formatCurrency(this.total()));
 
+  protected toggleEditing(): void {
+    if (this.editingDisabled()) {
+      return;
+    }
+
+    const editing = !this.editing();
+    this.editing.set(editing);
+  }
+
   private formatCurrency(value: number): string {
     const rounded = Math.round(value);
     const parts = rounded.toString().split('.');