fix(talkbot): convert incoming audio to WAV before transcription

containers/talkbot/talkbot.Containerfile

@@ -10,7 +10,7 @@ USER root
 EXPOSE 8100
 
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends curl \
+    && apt-get install -y --no-install-recommends curl ffmpeg \
     && apt-get autoremove -y \
     && apt-get clean -y \
     && rm -rf /var/lib/apt/lists/*