compose: opt-in trunk-recorder service + supervisor and uploadScript (node-26#45)

robotastic/trunk-recorder:5.2.1 pinned by digest, behind the
trunk-recorder compose profile, host network, /dev/bus/usb. run.sh
restarts TR when the edge-node rewrites config.json and reports state
for health; drb-upload.sh hands each finished call (wav, then json) to
recordings/tr-inbox. README carries the GPL-3.0 source note.

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

trunk-recorder/README.md

@@ -0,0 +1,34 @@
+# Trunk Recorder on a DRB node (node-26#45)
+
+Opt-in alternative to the OP25 recorder. On a node, set both in `.env`, then
+`docker compose up -d`:
+
+    RECORDER_BACKEND=trunk-recorder
+    COMPOSE_PROFILES=trunk-recorder
+
+Set both back (`RECORDER_BACKEND=op25`, remove `COMPOSE_PROFILES`) to return
+to OP25.
+
+- `run.sh`: supervisor that replaces the image's CMD. It restarts TR when the
+  edge-node rewrites `configs/trunk-recorder/config.json`, and writes
+  `drb-status.json` for the dashboard health check.
+- `drb-upload.sh`: TR's `uploadScript`. It copies each finished call (WAV +
+  JSON) into `recordings/tr-inbox`, where the edge-node uploads it through the
+  normal spool.
+
+## License (GPL-3.0)
+
+Trunk Recorder is GPL-3.0. DRB runs the unmodified upstream image
+`robotastic/trunk-recorder:5.2.1` (digest pinned in `docker-compose.yml`) as a
+separate program. It talks to DRB only through files, a script argument list
+and a local UDP socket. That makes it mere aggregation, the same position we
+already hold for OP25.
+
+Anyone we distribute a node image or device to must still be able to get the
+corresponding source. Upstream source for this exact version is at
+<https://github.com/TrunkRecorder/trunk-recorder/tree/v5.2.1>. If we ever ship
+the TR image ourselves (mirrored to our registry, preinstalled on a sold
+device), we must also offer that source directly, in writing, for three years,
+or ship it alongside. Pointing to upstream alone is not enough at that point.
+Any patch to TR itself makes DRB's copy a modified version, which must then be
+published under GPL-3.0.