Adopt b2b.next's client patterns: services, page state, feedback

Ported from the owner's b2b.next and adapted from MudBlazor to the daisyUI
components:
- LocalizableComponentBase provides CascadingState, Navigation, Toast,
  IsLoading/IsDefaultDisabled, WhenOnline/StartOnlinePolling, and after-render
  jobs that actually run.
- CascadingState starts with initialised state and polls the online status
  with a PeriodicTimer. It reports errors through ILoggingService plus a toast,
  and disposes what it holds.
- New pieces:
  - ToastService + ToastHost, the snackbar, with AddResponseError/Success/
    Warning/Exception in SUtility;
  - ErrorViewer, which shows the validation messages plus AdditionalError(s);
  - LoggingService, which writes to the console and the IndexedDB client log.
- HttpService is rebuilt and registered:
  - auth levels Get/Post/Delete, *Anon and *TotallyAnon;
  - retry with backoff;
  - classified failures (FailureCodes) instead of exceptions;
  - HTTP 410 on cancel;
  - the "default" client.
  ReadWebResult and DefaultReadFromJsonAsync read its responses.
- ClientJsonContext is source-generated, and SUtility.DefaultSerializer and
  Blazored.LocalStorage use it.
- WebResult gains a C# 14 IsInvalid extension property.

The code follows the imported rules:
- Every service and async helper takes a CancellationToken last.
- Primary constructors replace constructor-plus-fields.
- MessagesService and IStorage return Task<WebResult> / Task<List<T>>.
  MessagesService is still mock, building its results in memory; the seed
  feed and thread moved to Faker.
- Index and ExpandMessage follow the page pattern: an offline guard with
  WhenOnline, LoadData, and early returns with toasts on the results they used
  to ignore. ExpandMessage reloads on route change and shows "not found"
  instead of a null message.
- Model and state collections are [], and the fake identity defaults moved
  out of the models.
- Components:
  - no ?. chains over initialised state;
  - [Inject] instead of @inject;
  - IsDefaultDisabled on the actions;
  - autocomplete on every text input;
  - Localizer[key, args] instead of string.Format;
  - the localizer no longer leaks its inner _pLocalizer.
- Settings → General gains a language picker (English/Italiano), and
  SetDefaultCulture limits the culture to those two.

Bugs fixed along the way:
- A compose with untouched (null) content passed the empty check.
- File errors were joined with <br/> and rendered as markup.
- ClientLogs.ErrorMessage() threw on warnings.
- CoalescingStringLocalizer[key, args] showed a raw "{0}" for missing keys.
- AppStatusService exposed a call to a JS function that doesn't exist.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

Components/Content.razor

@@ -3,7 +3,7 @@
 <div class="flex gap-3 w-full rounded-xl neo-raised @(Highlighted ? "neo-sm" : "neo-2xs") @CssContainer">
 
 	<div class="flex flex-col py-3 pl-3 md:py-4 md:pl-4 flex-none rounded-l-xl bg-cover bg-no-repeat bg-center"
-			 style="background-image:linear-gradient(to left, var(--color-base-100), transparent), url('@(Message.User?.BackgroundUrl)');">
+			 style="background-image:linear-gradient(to left, var(--color-base-100), transparent), url('@(Message.User.BackgroundUrl)');">
 
 		<a class="block h-12 w-12 md:h-16 md:w-16" href="@Message.User.ProfileUrl" title="@Message.User.UserName">
 			<img alt="@Message.User.UserName" class="h-12 w-12 md:h-16 md:w-16 object-cover rounded-full neo-raised neo-2xs" src="@(Message.User.PictureUrl ?? "/imgs/icon-192.png")" />
@@ -32,8 +32,8 @@
 					</a>
 				</span>
 				<span class="flex-none inline-flex gap-1 items-center">
-					<span title="@Message.CreatedAt.ToLocalTime().ToString("📅dd/MM/yy 🕒HH:mm")">
-						@Message.CreatedAt.GetPassedTime(Localizer._pLocalizer)
+					<span title="@Message.CreatedAt.ToLocalTime().ToString(SUtility.dateTimeFormatExt)">
+						@Message.CreatedAt.GetPassedTime(Localizer)
 					</span>
 					<i aria-hidden="true" class="@Message.MessageType.GetMessageTypeIcon() text-base"
 						 title="@Localizer[Message.MessageType.ToString()]">
@@ -104,13 +104,13 @@
 			<div class="flex gap-3">
 				@if (OnMessageReply.HasDelegate)
 				{
-					<DButton Size="DSize.Sm" Active="isAnswering" OnClick="Reply" title="@Localizer[isAnswering ? "Close" : "Reply"]">
+					<DButton Size="DSize.Sm" Active="isAnswering" Disabled="IsDefaultDisabled" OnClick="Reply" title="@Localizer[isAnswering ? "Close" : "Reply"]">
 						<i aria-hidden="true" class="@SUtility.IfTrueThen(isAnswering, "ion-md-close-circle", "ion-md-text") text-lg text-success"></i>
 					</DButton>
 				}
 				@if (OnMessageBoost.HasDelegate)
 				{
-					<DButton Size="DSize.Sm" Active="Message.IsBoostedByCurrentUser" OnClick="() => OnMessageBoost.InvokeAsync(Message)"
+					<DButton Size="DSize.Sm" Active="Message.IsBoostedByCurrentUser" Disabled="IsDefaultDisabled" OnClick="() => OnMessageBoost.InvokeAsync(Message)"
 							 title="@Localizer["Boost"]">
 						<i aria-hidden="true" class="ion-md-repeat @SUtility.IfTrueThen(Message.BoostsCounter != 0, null, "text-lg") text-info"></i>
 						@if (Message.BoostsCounter != 0)
@@ -121,7 +121,7 @@
 				}
 				@if (OnMessageFavourite.HasDelegate)
 				{
-					<DButton Size="DSize.Sm" Active="Message.IsFavourite" OnClick="() => OnMessageFavourite.InvokeAsync(Message)"
+					<DButton Size="DSize.Sm" Active="Message.IsFavourite" Disabled="IsDefaultDisabled" OnClick="() => OnMessageFavourite.InvokeAsync(Message)"
 							 title="@Localizer["Favourite"]">
 						<i aria-hidden="true" class="@SUtility.IfTrueThen(Message.IsFavourite, "ion-md-heart-dislike", "ion-md-heart") text-lg text-pink-300"></i>
 					</DButton>
@@ -138,28 +138,29 @@
 					<ChildContent>
 						@if (OnUserDirectMessage.HasDelegate)
 						{
-							<DButton Size="DSize.Sm" class="justify-start whitespace-nowrap" OnClick="() => OnUserDirectMessage.InvokeAsync(Message)">
+							<DButton Size="DSize.Sm" class="justify-start whitespace-nowrap" Disabled="IsDefaultDisabled" OnClick="() => OnUserDirectMessage.InvokeAsync(Message)">
 								<i aria-hidden="true" class="ion-md-paper-plane text-base text-success"></i>
 								<span>@Localizer["Direct message"]</span>
 							</DButton>
 						}
 						@if (OnUserSilence.HasDelegate)
 						{
-							<DButton Size="DSize.Sm" class="justify-start whitespace-nowrap" OnClick="() => OnUserSilence.InvokeAsync(Message.User)">
+							<DButton Size="DSize.Sm" class="justify-start whitespace-nowrap" Disabled="IsDefaultDisabled" OnClick="() => OnUserSilence.InvokeAsync(Message.User)">
 								<i aria-hidden="true" class="ion-md-eye-off text-base drop-shadow-sm text-warning"></i>
 								<span>@Localizer["Mute"]</span>
 							</DButton>
 						}
 						@if (OnUserBlock.HasDelegate)
 						{
-							<DButton Size="DSize.Sm" class="justify-start whitespace-nowrap" OnClick="() => OnUserBlock.InvokeAsync(Message.User)">
+							<DButton Size="DSize.Sm" class="justify-start whitespace-nowrap" Disabled="IsDefaultDisabled" OnClick="() => OnUserBlock.InvokeAsync(Message.User)">
 								<i aria-hidden="true" class="ion-md-remove-circle text-base text-error"></i>
 								<span>@Localizer["Block"]</span>
 							</DButton>
 						}
-						@if (@*Message.User.UserName == CurrentUserName &&*@ OnMessageDelete.HasDelegate)
+						@* Once signed in for real: only for the author's own messages (Message.User.UserId == CascadingState.User.Id). *@
+						@if (OnMessageDelete.HasDelegate)
 						{
-							<DButton Size="DSize.Sm" class="justify-start whitespace-nowrap" OnClick="DeleteMessage" title="@Localizer["Delete"]">
+							<DButton Size="DSize.Sm" class="justify-start whitespace-nowrap" Disabled="IsDefaultDisabled" OnClick="DeleteMessage" title="@Localizer["Delete"]">
 								<i aria-hidden="true" class="ion-md-trash text-lg text-error"></i>
 								<span>@Localizer["Delete"]</span>
 							</DButton>
@@ -184,8 +185,6 @@
 </div>
 
 @code {
-	[CascadingParameter] Task<AuthenticationState> AuthState { get; set; }
-	[CascadingParameter] CascadingState CascadingState { get; set; }
 	[Parameter] public Message Message { get; set; } = new();
 	[Parameter] public EventCallback<MessageForm> OnMessageReply { get; set; }
 	[Parameter] public EventCallback<Message> OnMessageBoost { get; set; }
@@ -200,15 +199,9 @@
 	[Parameter] public bool Highlighted { get; set; }
 	[Parameter] public bool IncludeExpand { get; set; } = true;
 
-	bool isAnswering { get; set; } = false;
+	bool isAnswering;
 
-	string CurrentUserName
-	{
-		get
-		{
-			return AuthState.Result.User.Identity?.Name;
-		}
-	}
+	protected override void OnInitialized() => IsLoading = false;
 
 	async Task DeleteMessage()
 	{
@@ -222,11 +215,8 @@
 		await OnMessageReply.InvokeAsync(messageForm);
 	}
 
-	async Task Reply()
+	void Reply()
 	{
-		await Task.Run(() =>
-		{
-		});
 		isAnswering = !isAnswering;
 	}
-}
+}