edge-node: Trunk Recorder backend behind RECORDER_BACKEND (node-26#45)

RECORDER_BACKEND=trunk-recorder (default op25, unchanged):
- tr_config: TR config.json + talkgroup/channel CSVs from the C2 system
  config (P25 trunked, P25 conventional, analog with squelch).
- tr_calls: TR call JSON -> MQTT call_start/call_end + /upload fields
  (talkgroup, start/stop, freq, units from srcList, emergency, encrypted).
- trunk_recorder: inbox ingest through the #44 spool with deterministic
  call_ids, supervisor requests, live audio via simplestream -> pacat ->
  drb_sink for Discord (one talkgroup at a time).
- radio_backend: start/stop dispatch so OP25 never grabs the SDR, and the
  OP25 watcher/PulseAudio recorder stay off (no double uploads).
- health/dashboard/checkin show the active backend and TR health.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-edge-node/app/internal/sdr_settings.py

@@ -83,7 +83,18 @@ async def set_sdr_settings(priority: Optional[Iterable[str]] = None,
         cfg.sdr_pins = normalize_sdr_pins(pins)
     save_node_config(cfg)
 
-    if cfg.sdr_pins.get("op25") != old_op25:
+    if cfg.sdr_pins.get("op25") != old_op25 and settings.recorder_backend == "trunk-recorder":
+        # Trunk Recorder takes the "op25" dongle (node-26#45): rewrite its
+        # config with the new serial; run.sh restarts it on the change.
+        from app.internal.health import active_config
+        from app.main import _generate_op25_config
+        await secondary_sdr_client.apply([], {}, [])
+        current = active_config(cfg)
+        if current is not None and await _generate_op25_config(current):
+            from app.internal import radio_backend
+            await radio_backend.start()  # waits until TR holds the new dongle
+        logger.info(f"Trunk Recorder moved to SDR {cfg.sdr_pins.get('op25') or 'rtl=0 (first dongle)'}")
+    elif cfg.sdr_pins.get("op25") != old_op25:
         from app.internal.op25_client import op25_client
         # Free the new dongle first if a decoder holds it, then move OP25.
         await secondary_sdr_client.apply([], {}, [])