feat: Add "Copy message ID" option to message context menu

src/EchoHub.Client/UI/MainWindow.cs

@@ -630,6 +630,7 @@ public sealed partial class MainWindow : Runnable
 
         if (line.MessageId is { } messageId)
         {
+            items.Add(new MenuItem("Copy message ID", "", () => CopyToClipboard(messageId.ToString()), Key.Empty));
             items.Add(new Line());
             items.Add(new MenuItem("Delete message", "", () => ConfirmDeleteMessage(messageId), Key.Empty));
         }

src/EchoHub.Server/Data/Migrations/20260715232856_AddChannelPasswordHash.cs

@@ -1,4 +1,4 @@
-using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
 

src/EchoHub.Server/Data/Migrations/20260716012917_AddChannelEncryptionEnvelope.cs

@@ -1,4 +1,4 @@
-using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable
 

src/EchoHub.Server/Data/Migrations/20260716020211_AddMessageAttachments.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using Microsoft.EntityFrameworkCore.Migrations;
 
 #nullable disable