feat: implement notification sound functionality with user customization options

src/EchoHub.Server/Controllers/ModerationController.cs

@@ -72,13 +72,17 @@ public class ModerationController : ControllerBase
         if (target.Role >= caller!.Role)
             return BadRequest(new ErrorResponse("Cannot kick a user with equal or higher role."));
 
-        // Broadcast kick to all channels the user is in
+        // Broadcast kick to all channels the user is in, then clean up presence
         var channels = _presenceTracker.GetChannelsForUser(target.Username);
         foreach (var channel in channels)
         {
             await BroadcastToAllAsync(b => b.SendUserKickedAsync(channel, target.Username, request?.Reason));
         }
 
+        // Remove from presence tracker and force disconnect all connections
+        var reason = request?.Reason ?? "You have been kicked from the server.";
+        await ForceDisconnectAndCleanupAsync(target.Username, reason);
+
         return Ok(new { Message = $"{target.Username} has been kicked." });
     }
 
@@ -98,8 +102,12 @@ public class ModerationController : ControllerBase
         target.IsBanned = true;
         await _db.SaveChangesAsync();
 
+        // Broadcast ban notification, then force disconnect
         await BroadcastToAllAsync(b => b.SendUserBannedAsync(target.Username, request?.Reason));
 
+        var reason = request?.Reason ?? "You have been banned from this server.";
+        await ForceDisconnectAndCleanupAsync(target.Username, reason);
+
         return Ok(new { Message = $"{target.Username} has been banned." });
     }
 
@@ -217,6 +225,36 @@ public class ModerationController : ControllerBase
         return (caller, null);
     }
 
+    /// <summary>
+    /// Remove user from presence tracking, broadcast their departure from all channels,
+    /// send a ForceDisconnect signal, and update their DB status.
+    /// </summary>
+    private async Task ForceDisconnectAndCleanupAsync(string username, string reason)
+    {
+        var (connectionIds, channels) = _presenceTracker.ForceRemoveUser(username);
+
+        // Notify remaining users that this person left each channel
+        foreach (var channel in channels)
+        {
+            await BroadcastToAllAsync(b => b.SendUserLeftAsync(channel, username));
+        }
+
+        // Signal the user's clients to disconnect
+        if (connectionIds.Count > 0)
+        {
+            await BroadcastToAllAsync(b => b.ForceDisconnectUserAsync(connectionIds, reason));
+        }
+
+        // Mark user offline in DB
+        var user = await _db.Users.FirstOrDefaultAsync(u => u.Username == username);
+        if (user is not null)
+        {
+            user.Status = UserStatus.Invisible;
+            user.LastSeenAt = DateTimeOffset.UtcNow;
+            await _db.SaveChangesAsync();
+        }
+    }
+
     private async Task BroadcastToAllAsync(Func<IChatBroadcaster, Task> action)
     {
         foreach (var broadcaster in _broadcasters)

src/EchoHub.Server/Services/PresenceTracker.cs

@@ -151,4 +151,27 @@ public class PresenceTracker
     {
         return _userConnections.Count;
     }
+
+    /// <summary>
+    /// Forcibly remove a user from all tracking. Returns their connection IDs and channels
+    /// so the caller can broadcast departures and force-disconnect connections.
+    /// </summary>
+    public (List<string> ConnectionIds, List<string> Channels) ForceRemoveUser(string username)
+    {
+        lock (_lock)
+        {
+            var channels = _userChannels.TryRemove(username, out var ch)
+                ? ch.ToList()
+                : [];
+
+            var connectionIds = _userConnections.TryRemove(username, out var conns)
+                ? conns.ToList()
+                : [];
+
+            foreach (var connId in connectionIds)
+                _connections.TryRemove(connId, out _);
+
+            return (connectionIds, channels);
+        }
+    }
 }

src/EchoHub.Server/Services/SignalRBroadcaster.cs

@@ -73,4 +73,13 @@ public class SignalRBroadcaster : IChatBroadcaster
 
         return HubContext.Clients.Client(connectionId).Error(message);
     }
+
+    public Task ForceDisconnectUserAsync(List<string> connectionIds, string reason)
+    {
+        var signalRIds = connectionIds.Where(c => !c.StartsWith("irc-")).ToList();
+        if (signalRIds.Count == 0)
+            return Task.CompletedTask;
+
+        return HubContext.Clients.Clients(signalRIds).ForceDisconnect(reason);
+    }
 }