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 Removed outdated bumper-related commands and handlers from the application, streamlining the codebase and improving maintainability.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/src/TeleWave.Application/Programming/Templates/Junctions/DeleteJunctionCommandHandler.cs

@@ -21,19 +21,19 @@ public sealed class DeleteJunctionCommandHandler(IAppDbContext dbContext)
         if (junction is null)
             return Result.Failure(TemplateErrors.JunctionNotFound);
 
-        // Слот, ссылающийся на удалённый стык, молча остался бы без врезок — проверяем заранее.
-        var used = await dbContext.Slots.AnyAsync(
+        // Стык общий: слот чужого канала, ссылающийся на удалённый стык, молча остался бы без врезок.
+        var usedBySlot = await dbContext.Slots.AnyAsync(
             s => s.JunctionBetweenId == junction.Id || s.JunctionAfterId == junction.Id,
             cancellationToken
         );
-        if (used)
+        var usedByDefault = await dbContext.ScheduleTemplates.AnyAsync(
+            t => t.DefaultJunctionId == junction.Id,
+            cancellationToken
+        );
+        if (usedBySlot || usedByDefault)
             return Result.Failure(TemplateErrors.JunctionInUse);
 
         dbContext.JunctionTemplates.Remove(junction);
-        return await JunctionLoader.MarkTemplateChangedAsync(
-            dbContext,
-            junction,
-            cancellationToken
-        );
+        return Result.Success();
     }
 }