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 Removed outdated bumper-related commands and handlers from the application, streamlining the codebase and improving maintainability.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.Application.Tests/Broadcast/ChannelHandlersTests.cs

@@ -48,14 +48,7 @@ public class ChannelHandlersTests
 
         await using var db = fixture.New();
         var result = await new UpdateChannelSettingsCommandHandler(db).Handle(
-            new UpdateChannelSettingsCommand(
-                channel.Id,
-                "c",
-                true,
-                true,
-                new BumperSettingsInput(BumperFont.Sans, BumperSelection.WeightedRandom),
-                null
-            ),
+            new UpdateChannelSettingsCommand(channel.Id, "c2", true, null),
             CancellationToken.None
         );
         Assert.True(result.IsSuccess);
@@ -63,7 +56,7 @@ public class ChannelHandlersTests
 
         await using var verify = fixture.New();
         var stored = await verify.Channels.FindAsync(channel.Id);
-        Assert.Equal(BumperFont.Sans, stored!.BumperFont);
-        Assert.Equal(BumperSelection.WeightedRandom, stored.BumperSelection);
+        Assert.Equal("c2", stored!.Name);
+        Assert.True(stored.IsEnabled);
     }
 }