feat(backend): add SIMPLE_STREAMING WebRTC control-path streaming

Backend/media/sfu/service.ts

@@ -1,8 +1,12 @@
-import { mediaMode } from '../config';
+import { mediaMode, simpleStreamingEnabled } from '../config';
 import { NoopSfuService } from './noop';
 import type { SfuService } from './types';
 
 const createSfuService = (): SfuService | null => {
+  if (simpleStreamingEnabled) {
+    return null;
+  }
+
   if (mediaMode !== 'single_server_sfu') {
     return null;
   }
@@ -11,4 +15,3 @@ const createSfuService = (): SfuService | null => {
 };
 
 export const sfuService = createSfuService();
-