feat: add password protection for channels

- Updated IChatService to include password parameter in JoinChannelAsync method.
- Modified ChannelDto and related models to support password functionality.
- Implemented password handling in ChannelService for channel creation and membership validation.
- Enhanced IrcCommandHandler to manage channel join requests with passwords.
- Added ChannelPasswordDialog for user input when joining protected channels.
- Created database migration to add PasswordHash column to Channels table.
- Updated tests to cover new password functionality in channel joining and management.

src/EchoHub.Core/DTOs/ChatDtos.cs

@@ -21,7 +21,8 @@ public record ChannelDto(
     string? Topic,
     bool IsPublic,
     int MessageCount,
-    DateTimeOffset CreatedAt);
+    DateTimeOffset CreatedAt,
+    bool IsProtected = false);
 
 public record UserDto(
     Guid Id,
@@ -33,13 +34,13 @@ public record UserDto(
 
 public record SendMessageRequest(string ChannelName, string Content);
 
-public record CreateChannelRequest(string Name, string? Topic = null, bool IsPublic = true);
+public record CreateChannelRequest(string Name, string? Topic = null, bool IsPublic = true, string? Password = null);
 
 public record UpdateTopicRequest(string? Topic);
 
 public record SendUrlRequest(string Url);
 
-public record JoinChannelResult(bool Success, List<MessageDto> History, string? Error = null);
+public record JoinChannelResult(bool Success, List<MessageDto> History, string? Error = null, bool PasswordRequired = false);
 
 public record EmbedDto(
     string? SiteName,