feat: enhance profile editing with avatar support and UI adjustments

- Added AvatarPath to ProfileEditResult for user profile updates.
- Updated ProfileEditDialog to include avatar selection with a browse button.
- Increased dialog height to accommodate new avatar input fields.
- Implemented avatar file path handling in the profile edit dialog.

feat: introduce moderation features and user roles

- Added ServerRole enum to define user roles (Member, Mod, Admin, Owner).
- Extended User model to include role, mute, and ban status.
- Created ModerationController for user role assignment, kicking, banning, and muting.
- Implemented methods in IChatBroadcaster and SignalRBroadcaster for user moderation actions.
- Updated database schema with new columns for user roles and moderation states.

fix: ensure muted users cannot send messages

- Added mute status checks in ChatService to prevent message sending for muted users.
- Updated user presence and status handling to reflect role changes and moderation actions.

chore: update constants for ASCII art rendering

- Introduced AsciiArtHeightHalfBlock constant for improved ASCII art rendering.

src/EchoHub.Server/Controllers/ChannelsController.cs

@@ -141,8 +141,10 @@ public class ChannelsController : ControllerBase
         if (dbChannel is null)
             return NotFound(new ErrorResponse($"Channel '{channelName}' does not exist."));
 
-        if (dbChannel.CreatedByUserId != Guid.Parse(userIdClaim))
-            return StatusCode(403, new ErrorResponse("Only the channel creator can delete the channel."));
+        var userId = Guid.Parse(userIdClaim);
+        var caller = await _db.Users.FindAsync(userId);
+        if (dbChannel.CreatedByUserId != userId && (caller is null || caller.Role < ServerRole.Admin))
+            return StatusCode(403, new ErrorResponse("Only the channel creator or an admin can delete the channel."));
 
         _db.Channels.Remove(dbChannel);
         await _db.SaveChangesAsync();