Add MQTT-based STT worker for VAD segments

bridge/README.md

@@ -8,6 +8,7 @@ It provides:
 - MQTT playback input (`evs/<device_id>/play_pcm16le`)
 - Optional Home Assistant webhook callbacks (`connected`, `start`, `stop`, `disconnected`)
 - VAD auto-segmentation (`vad_segment`) with pre-roll/post-roll
+- Optional STT worker (`vad_segment` -> `transcript`) via MQTT
 
 ## 1) Start the bridge
 
@@ -53,7 +54,7 @@ Then upload firmware.
 
 1. Flash ESP32
 2. Open serial monitor
-3. Send `s` (stream mode)
+3. Wait for WS connect (client switches to stream mode automatically)
 4. In bridge logs, you should see the device connection
 5. If `ECHO_ENABLED=true`, incoming audio is returned to ESP32 speaker
 
@@ -63,7 +64,8 @@ Then upload firmware.
   - `evs/<device_id>/status` (connection/start/stop/disconnect)
   - `evs/<device_id>/mic_level` (mic telemetry)
   - `evs/<device_id>/vad_segment` (finalized speech segments)
-  - reserved for next steps: `evs/<device_id>/transcript`, `evs/<device_id>/stt_error`
+  - `evs/<device_id>/transcript` (text from stt-worker)
+  - `evs/<device_id>/stt_error` (stt-worker errors)
 - Playback input to device:
   - `evs/<device_id>/play_pcm16le`
   - payload options:
@@ -101,6 +103,20 @@ You can build automations on these events (for STT/TTS pipelines or Node-RED han
   - `VAD_KEEP_FILES=200` limits number of stored VAD WAV files
   - `VAD_MAX_AGE_DAYS=7` deletes VAD WAV files older than 7 days
 - MQTT is recommended for control/events, WebSocket for streaming audio
+- STT worker:
+  - subscribes: `evs/<device_id>/vad_segment`
+  - reads `wav_path` from event JSON
+  - transcribes with `faster-whisper`
+  - publishes transcript to `evs/<device_id>/transcript`
+
+## 6.1) STT Worker Config
+
+Use these env values (in `.env` or Portainer):
+- `STT_MODEL` (`tiny`, `base`, `small`, `medium`, `large-v3`)
+- `STT_DEVICE` (`cpu` or `cuda`)
+- `STT_COMPUTE_TYPE` (`int8`, `float16`, ...)
+- `STT_LANGUAGE` (`de` or empty for auto-detect)
+- `MQTT_VAD_TOPIC`, `MQTT_TRANSCRIPT_TOPIC_TEMPLATE`, `MQTT_STT_ERROR_TOPIC_TEMPLATE`
 
 ## 7) Build and push to Gitea registry
 
@@ -161,6 +177,29 @@ services:
     volumes:
       - evs_bridge_data:/data
 
+  evs-stt-worker:
+    image: git.khnm-zimmerling.de/kai/evs-stt-worker:latest
+    container_name: evs-stt-worker
+    restart: unless-stopped
+    environment:
+      LOG_LEVEL: "INFO"
+      MQTT_HOST: "10.100.3.247"
+      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"
+    volumes:
+      - evs_bridge_data:/data
+
 volumes:
   evs_bridge_data:
 ```