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

Services/MessagesService.cs

@@ -1,74 +1,88 @@
-using decePubClient.Models;
+using collAnon.Client.Services;
+
+using decePubClient.Extensions;
+using decePubClient.Models;
 using decePubClient.Models.Types;
 
+using PrivaPub.ClientModels;
+
 namespace decePubClient.Services
 {
-	public class MessagesService
+	/// <summary>
+	/// Message actions. Still a mock: the app isn't wired to PrivaPub yet, so each method builds its result in memory.
+	/// The signatures are the real ones (a Task&lt;WebResult&gt; whose Data is the updated entity), so wiring means
+	/// calling httpService against PrivaPub's /clientapi/post/* routes inside the same try/catch, reading failures with
+	/// ReadWebResult and the body with DefaultReadFromJsonAsync, as b2b.next's StoreService does.
+	/// </summary>
+	public class MessagesService(ILoggingService logger, CoalescingStringLocalizer localizer)
 	{
-		readonly IStorage storage;
-		readonly HttpClient http;
+		/// <summary>Posts a message or, with RootMessageId set, a reply; Data is the new Message.</summary>
+		public Task<WebResult> SubmitMessage(MessageForm messageForm, User author, CancellationToken cancellationToken = default) =>
+			Run(nameof(SubmitMessage), () => (object)new Message
+			{
+				RootMessageId = messageForm.RootMessageId,
+				MessageId = Guid.NewGuid().ToString(),
+				Content = messageForm.Content?.ParseContent(messageForm.ContentType),
+				CreatedAt = DateTime.UtcNow,
+				MessageType = messageForm.MessageType,
+				Medias = [.. messageForm.Media.Select(m => new Media
+				{
+					FileName = m.FileName,
+					AltText = m.AltText,
+					ContentType = m.ContentType,
+					Url = m.Base64Preview,
+					Blob = m.Blob
+				})],
+				Title = messageForm.Title,
+				User = author.ToMessageUser()
+			}, cancellationToken);
 
-		public MessagesService(IHttpClientFactory clientFactory, IStorage storage)
+		/// <summary>Opens a reply of the given scope to a message; Data is the message.</summary>
+		public Task<WebResult> ReplyMessage(Message messageToReply, MessageType messageType = MessageType.Public, CancellationToken cancellationToken = default) =>
+			Run(nameof(ReplyMessage), () => messageToReply, cancellationToken);
+
+		/// <summary>Boosts the message, or takes the boost back; Data is the message with its counter updated.</summary>
+		public Task<WebResult> BoostUnboostMessage(Message message, CancellationToken cancellationToken = default) =>
+			Run(nameof(BoostUnboostMessage), () =>
+			{
+				message.BoostsCounter += message.IsBoostedByCurrentUser ? -1 : 1;
+				message.IsBoostedByCurrentUser = !message.IsBoostedByCurrentUser;
+				return message;
+			}, cancellationToken);
+
+		/// <summary>Adds the message to the favourites, or removes it; Data is the updated message.</summary>
+		public Task<WebResult> FavouriteUnfavouriteMessage(Message message, CancellationToken cancellationToken = default) =>
+			Run(nameof(FavouriteUnfavouriteMessage), () =>
+			{
+				message.IsFavourite = !message.IsFavourite;
+				return message;
+			}, cancellationToken);
+
+		public Task<WebResult> DeleteMessage(Message message, CancellationToken cancellationToken = default) =>
+			Run(nameof(DeleteMessage), () => message, cancellationToken);
+
+		public Task<WebResult> BlockUserFromMessage(MessageUser messageUser, CancellationToken cancellationToken = default) =>
+			Run(nameof(BlockUserFromMessage), () => messageUser, cancellationToken);
+
+		public Task<WebResult> SilenceUserFromMessage(MessageUser messageUser, CancellationToken cancellationToken = default) =>
+			Run(nameof(SilenceUserFromMessage), () => messageUser, cancellationToken);
+
+		/// <summary>The mock's stand-in for an API call: the same success/failure handling, with the outcome built locally.</summary>
+		async Task<WebResult> Run(string caller, Func<object> action, CancellationToken cancellationToken)
 		{
-			this.storage = storage;
-			http = clientFactory.CreateClient("default");
-		}
-
-		//Covers also direct message
-		public async Task<Message> SubmitMessage(MessageForm messageForm)
-		{
-			//TODO
-
-			await Task.Run(() => {});
-			return new();
-		}
-
-		//Covers also direct message
-		public async Task<Message> ReplyMessage(Message messageToReply, MessageType messageType = MessageType.Public)
-		{
-			//TODO
-
-			await Task.Run(() => {});
-			return messageToReply;
-		}
-
-		public async Task<Message> BoostUnboostMessage(Message messageToReply)
-		{
-			//TODO
-
-			await Task.Run(() => {});
-			return messageToReply;
-		}
-
-		public async Task<Message> FavouriteUnfavouriteMessage(Message messageToReply)
-		{
-			//TODO
-
-			await Task.Run(() => {});
-			return messageToReply;
-		}
-
-		public async Task<Message> DeleteMessage(Message messageToReply)
-		{
-			//TODO
-
-			await Task.Run(() => {});
-			return messageToReply;
-		}
-
-		public async Task<MessageUser> BlockUserFromMessage(MessageUser messageUser)
-		{
-			//TODO
-			await Task.Run(() => {});
-			return messageUser;
-		}
-
-		public async Task<MessageUser> SilenceUserFromMessage(MessageUser messageUser)
-		{
-			//TODO
-
-			await Task.Run(() => {});
-			return messageUser;
+			var result = new WebResult();
+			try
+			{
+				cancellationToken.ThrowIfCancellationRequested();
+				await Task.Yield();
+				result.Data = action();
+				return result;
+			}
+			catch (Exception ex)
+			{
+				await logger.ProcessError(ex, $"{nameof(MessagesService)}.{caller}", cancellationToken);
+				return result.Invalidate(localizer["The action could not be completed."], exception: ex);
+			}
 		}
 	}
-}
+}