feat: full FrontOffice updates - discount store, blog, payment gateway, UI improvements

- Discount store pages (products, cart, orders, order detail)
- Blog pages and services
- Payment gateway callback page
- AppImage component, EmptyState, LoadingState, PageHeader
- DiscountCartService, DiscountOrderService, DiscountProductService
- BlogCategoryService, BlogPostService, SitePageService, ImageCacheService
- PhoneVerifyForm component
- Profile Hub page
- UI/UX improvements across all pages
- landing.js for homepage
- Config and routing updates

src/FrontOffice.Main/Shared/LoadingState.razor

@@ -0,0 +1,18 @@
+@* ═══════════════════════════════════════════════
+   LoadingState — Unified loading indicator
+   Usage: <LoadingState />
+          <LoadingState Message="در حال دریافت سفارشات..." />
+   ═══════════════════════════════════════════════ *@
+
+<MudStack AlignItems="AlignItems.Center" Class="py-16">
+    <MudProgressCircular Color="Color.Primary" Indeterminate="true" Size="Size.Large" />
+    @if (!string.IsNullOrWhiteSpace(Message))
+    {
+        <MudText Typo="Typo.body1" Class="mud-text-secondary mt-2">@Message</MudText>
+    }
+</MudStack>
+
+@code {
+    /// <summary>Optional loading message displayed below spinner.</summary>
+    [Parameter] public string Message { get; set; } = "در حال بارگذاری...";
+}