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

Backend/media/service.ts

@@ -1,5 +1,6 @@
+import { simpleStreamingEnabled } from './config';
 import { MockMediaProvider } from './providers/mock';
-import type { MediaProvider } from './types';
+import type { MediaProvider, MediaSessionCreateInput, MediaSessionCreateResult } from './types';
 
 const providerName = (process.env.MEDIA_PROVIDER ?? 'mock').toLowerCase();
 
@@ -13,3 +14,14 @@ const createProvider = (): MediaProvider => {
 };
 
 export const mediaProvider = createProvider();
+export const mediaProviderRuntimeEnabled = !simpleStreamingEnabled;
+
+export const createLiveMediaSession = async (
+  input: MediaSessionCreateInput,
+): Promise<MediaSessionCreateResult | null> => {
+  if (!mediaProviderRuntimeEnabled) {
+    return null;
+  }
+
+  return mediaProvider.createSession(input);
+};