Implement BumperEndpoints and remove deprecated bumper-related functionality

Added new BumperEndpoints to the API for managing bumper templates and variants, enhancing the channel management capabilities. Removed outdated bumper-related commands and handlers from the application, streamlining the codebase and improving maintainability. Updated ChannelEndpoints to reflect these changes and ensure proper routing for the new endpoints.

backend/tests/TeleWave.Domain.Tests/Broadcast/BumperTemplateTests.cs

@@ -5,8 +5,7 @@ namespace TeleWave.Domain.Tests.Broadcast;
 
 public class BumperTemplateTests
 {
-    private static BumperTemplate NewTemplate() =>
-        Channel.Create("c", "c", DateTimeOffset.UnixEpoch).AddBumperTemplate("Block");
+    private static BumperTemplate NewTemplate() => BumperTemplate.Create("Block", "Текст 1");
 
     [Fact]
     public void Create_HasDefaultsAndOneVariant()
@@ -53,12 +52,17 @@ public class BumperTemplateTests
     {
         var t = NewTemplate();
 
-        t.UpdateStyle("New", "0x111111", "0x222222", "0x333333", "black");
+        t.UpdateStyle(
+            new BumperStyle("New", BumperFont.Serif, "0x111111", "0x222222", "0x333333", "black")
+        );
 
         Assert.Equal("New", t.Name);
+        Assert.Equal(BumperFont.Serif, t.Font);
         Assert.Equal("0x111111", t.BackgroundColor);
         Assert.Equal("0x333333", t.AccentColor);
         Assert.Equal("black", t.TextColor);
+        // Оформление входит в сигнатуру рендера — правка обязана пересобрать заставки.
+        Assert.Equal(1, t.Revision);
     }
 
     [Fact]