fix: menu item/category create, demo banner reach, token refresh, blog publish

Dashboard & API bug fixes for owner-reported breakage:

- MenuController validators (PosValidators): NameEn was required but the
  dashboard sends null when blank, so every manual menu-item create failed
  and category create failed 100% (the form never sends nameEn). Now optional.
- DemoDataBanner: only showed when a cafe was exactly empty, so
  showcase-seeded cafes (2-3 cats / 3-5 items) could never trigger the
  one-click seed. Widened gate to sparse menus (<5 cats && <10 items) and
  added a clear "nothing to add" message when already populated.
- client.ts: added one-time JWT refresh-and-retry on 401 (shared in-flight
  promise) before bouncing to /login. Expired access tokens silently broke
  ticket list, add-table, and other reads.
- Surface API errors as toasts on menu + table mutations (were swallowed
  silently, so failures looked like "nothing happens").
- Admin blog editor: saving an edit dropped IsPublished (defaulted false,
  silently unpublishing the post on every save); now persisted with a
  toggle. Also hoisted the inner Field component to module scope - it was
  remounting every input on each keystroke and dropping focus.
- Admin integrations: replaced raw radio gateway selector with a styled
  RadioDot matching the iOS toggles.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Meezi.API/Validators/PosValidators.cs

@@ -12,7 +12,7 @@ public class CreateMenuCategoryRequestValidator : AbstractValidator<CreateMenuCa
     public CreateMenuCategoryRequestValidator()
     {
         RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
-        RuleFor(x => x.NameEn).NotEmpty().MaximumLength(200);
+        RuleFor(x => x.NameEn).MaximumLength(200).When(x => !string.IsNullOrWhiteSpace(x.NameEn));
         RuleFor(x => x.SortOrder).GreaterThanOrEqualTo(0);
         RuleFor(x => x.DiscountPercent).InclusiveBetween(0, 100);
         RuleFor(x => x.Icon).MaximumLength(32).When(x => x.Icon is not null);
@@ -39,7 +39,7 @@ public class CreateMenuItemRequestValidator : AbstractValidator<CreateMenuItemRe
     {
         RuleFor(x => x.CategoryId).NotEmpty();
         RuleFor(x => x.Name).NotEmpty().MaximumLength(200);
-        RuleFor(x => x.NameEn).NotEmpty().MaximumLength(200);
+        RuleFor(x => x.NameEn).MaximumLength(200).When(x => !string.IsNullOrWhiteSpace(x.NameEn));
         RuleFor(x => x.Price).GreaterThanOrEqualTo(0);
         RuleFor(x => x.DiscountPercent).InclusiveBetween(0, 100);
     }