feat: Add notification sound functionality and embed support

- Introduced NotificationConfig to manage notification settings, including sound file.
- Added Notification.mp3 asset for notifications.
- Implemented NotificationSoundService to handle playing notification sounds.
- Enhanced ChatRenderer and MainWindow to support emoji rendering.
- Updated MessageDto to allow multiple embeds per message.
- Modified LinkEmbedService to fetch multiple embeds from message content.
- Added data migration for legacy embed JSON format to new array format.
- Adjusted embed handling in ChatService and IrcMessageFormatter to accommodate multiple embeds.
- Updated HubConstants for new embed dimensions and limits.

src/EchoHub.Server.Irc/IrcMessageFormatter.cs

@@ -24,9 +24,12 @@ public static partial class IrcMessageFormatter
                 foreach (var chunk in SplitMessage(message.Content, MaxIrcLineContentBytes))
                     lines.Add($"{prefix} PRIVMSG {ircChannel} :{chunk}");
 
-                // Append embed preview if present
-                if (message.Embed is not null)
-                    lines.AddRange(FormatEmbed(prefix, ircChannel, message.Embed));
+                // Append embed previews if present
+                if (message.Embeds is { Count: > 0 })
+                {
+                    foreach (var embed in message.Embeds)
+                        lines.AddRange(FormatEmbed(prefix, ircChannel, embed));
+                }
                 break;
 
             case MessageType.Image: