Added MP4 audio embeds for Discord in AudioEmbed.py

Dockerfile

@@ -7,6 +7,8 @@ RUN npm run build
 
 FROM python:3.12-slim
 WORKDIR /App
+# ffmpeg turns shared audio into MP4 for link embeds (Backend/AudioEmbed.py).
+RUN apt-get update && apt-get install -y --no-install-recommends ffmpeg && rm -rf /var/lib/apt/lists/*
 COPY Backend/requirements.txt ./
 RUN pip install --no-cache-dir -r requirements.txt
 # Headless Chromium for drawing the desktop client's diagrams (Backend/Diagrams.py).