fix: add ffmpeg to docker image

dockerfile

@@ -10,7 +10,7 @@ RUN npm run build
 # prod
 FROM node:24-alpine
 WORKDIR /app
-RUN apk add --no-cache python3 make g++
+RUN apk add --no-cache python3 make g++ ffmpeg
 COPY package*.json ./
 RUN npm ci --only=production   # only prod deps
 COPY --from=builder /app/dist ./dist

src/modules/audioStreams.ts

@@ -143,7 +143,8 @@ export class MixedStream {
 				}, durationMs);
 			});
 
-			transcoder.on('error', () => {
+			transcoder.on('error', (err) => {
+				console.error('Transcoder error:', err);
 				this.mixer.removeAudioinput(mixerInput);
 				resolve();
 			});