Add MQTT-based STT worker for VAD segments

stt-worker/Dockerfile

@@ -0,0 +1,26 @@
+FROM python:3.11-slim
+
+WORKDIR /app
+
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+
+COPY app.py .
+
+ENV LOG_LEVEL=INFO \
+    MQTT_HOST=localhost \
+    MQTT_PORT=1883 \
+    MQTT_USER= \
+    MQTT_PASSWORD= \
+    MQTT_BASE_TOPIC=evs \
+    MQTT_VAD_TOPIC=evs/+/vad_segment \
+    MQTT_TRANSCRIPT_TOPIC_TEMPLATE=evs/{device_id}/transcript \
+    MQTT_STT_ERROR_TOPIC_TEMPLATE=evs/{device_id}/stt_error \
+    STT_MODEL=small \
+    STT_DEVICE=cpu \
+    STT_COMPUTE_TYPE=int8 \
+    STT_BEAM_SIZE=1 \
+    STT_LANGUAGE=de \
+    STT_CONDITION_ON_PREV_TEXT=false
+
+CMD ["python", "app.py"]