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 Removed outdated bumper-related commands and handlers from the application, streamlining the codebase and improving maintainability.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.

frontend/src/features/admin/channels/ChannelDetail.tsx

@@ -19,7 +19,6 @@ import {
   restoreChannelTemplate,
 } from './api'
 import { ApplyDialog } from './components/ApplyDialog'
-import { BumperCard } from './components/BumperCard'
 import { EntryTraceDialog } from './components/EntryTraceDialog'
 import { GridTab } from './components/GridTab'
 import { JunctionsCard } from './components/JunctionsCard'
@@ -29,7 +28,7 @@ import { SettingsCard } from './components/SettingsCard'
 import { ViewerCard } from './components/ViewerCard'
 
 /** Вкладки экрана канала: настройки первыми — с них канал и начинается. */
-const TABS = ['settings', 'grid', 'rules', 'junctions', 'bumpers', 'viewer', 'air'] as const
+const TABS = ['settings', 'grid', 'rules', 'junctions', 'viewer', 'air'] as const
 type ChannelTab = (typeof TABS)[number]
 
 export function ChannelDetail({ channelId }: Readonly<{ channelId: string }>) {
@@ -180,17 +179,7 @@ export function ChannelDetail({ channelId }: Readonly<{ channelId: string }>) {
         ))}
 
       {tab === 'junctions' && (
-        <JunctionsCard
-          channel={channel}
-          template={template}
-          bare
-          onChanged={invalidate}
-          onError={onError}
-        />
-      )}
-
-      {tab === 'bumpers' && (
-        <BumperCard channel={channel} bare onSaved={invalidate} onError={onError} />
+        <JunctionsCard template={template} bare onChanged={invalidate} onError={onError} />
       )}
 
       {tab === 'viewer' && (