Refactor Channel endpoints and data models: replace jingle functionality with bumper templates, update related commands and handlers, and enhance API routes for managing bumper templates. Remove obsolete jingle-related code and adjust channel data structures to support new bumper template features.

backend/src/TeleWave.Application/Broadcast/Bumpers/SetBumperTemplateAudioCommand.cs

@@ -0,0 +1,12 @@
+using LiteCqrs;
+using TeleWave.Application.Common.Models;
+
+namespace TeleWave.Application.Broadcast.Bumpers;
+
+/// <summary>Отметить загруженный звук блока: расширение (с точкой) и длину в секундах (замер ffprobe).</summary>
+public sealed record SetBumperTemplateAudioCommand(
+    Guid ChannelId,
+    Guid TemplateId,
+    string Extension,
+    double DurationSeconds
+) : ICommand<Result>;