feat: add support for broadcasting and handling channel deletions across clients

src/EchoHub.Server/Controllers/ChannelsController.cs

@@ -162,6 +162,8 @@ public class ChannelsController : ControllerBase
         if (!result.IsSuccess)
             return MapChannelError(result);
 
+        await _chatService.BroadcastChannelDeletedAsync(channel.ToLowerInvariant().Trim());
+
         return NoContent();
     }
 

src/EchoHub.Server/Services/ChatService.cs

@@ -320,6 +320,9 @@ public class ChatService : IChatService
     public Task BroadcastChannelUpdatedAsync(ChannelDto channel, string? channelName = null)
         => BroadcastToAllAsync(b => b.SendChannelUpdatedAsync(channel, channelName));
 
+    public Task BroadcastChannelDeletedAsync(string channelName)
+        => BroadcastToAllAsync(b => b.SendChannelDeletedAsync(channelName));
+
     private async Task BroadcastToAllAsync(Func<IChatBroadcaster, Task> action)
     {
         foreach (var broadcaster in _broadcasters)

src/EchoHub.Server/Services/SignalRBroadcaster.cs

@@ -63,6 +63,9 @@ public class SignalRBroadcaster : IChatBroadcaster
     public Task SendMessageDeletedAsync(string channelName, Guid messageId)
         => HubContext.Clients.Group(channelName).MessageDeleted(channelName, messageId);
 
+    public Task SendChannelDeletedAsync(string channelName)
+        => HubContext.Clients.All.ChannelDeleted(channelName);
+
     public Task SendChannelNukedAsync(string channelName)
         => HubContext.Clients.Group(channelName).ChannelNuked(channelName);