Add EVS control portal, io_mode switching, and DAC-only speaker path

bridge/README.md

@@ -9,6 +9,7 @@ It provides:
 - 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
+- Optional 1:1 device pairing (`mic_device -> speaker_device`) for echo routing
 
 ## 1) Start the bridge
 
@@ -47,6 +48,11 @@ In `include/secrets.h`:
 - set bridge host
 - set WS port/path
 - set unique `EVS_DEVICE_ID`
+- set runtime IO mode:
+  - `EVS_DEFAULT_IO_MODE "mic"` for microphone device
+  - `EVS_DEFAULT_IO_MODE "spk"` for speaker device
+- set DAC output pin on speaker device:
+  - `EVS_SPK_DAC_PIN 25` or `26`
 
 Then upload firmware.
 
@@ -160,6 +166,7 @@ services:
       MQTT_BASE_TOPIC: "evs"
       MQTT_TTS_TOPIC: "evs/+/play_pcm16le"
       MQTT_STATUS_RETAIN: "true"
+      DEVICE_PAIR_MAP: '{"esp32-evs-1-mic":"esp32-evs-1-spk"}'
       HA_WEBHOOK_URL: ""
       SAVE_SESSIONS: "true"
       SESSIONS_DIR: "/data/sessions"