Mount the worker source in dev so it cannot fall behind the engine

The engine and the worker speak a version-matched protocol, but compose.dev.yml
mounted only backend/fluksio: a reloaded engine talked to the worker baked into
the image. Adding the request id to that protocol therefore left every python
node failing with "the worker answered request None", because the old worker
echoed no id at all.

docker/compose.dev.yml

@@ -112,6 +112,11 @@ services:
       # sync above — only `docker compose watch` does. Without the mount the
       # container serves the source baked into the image until it is rebuilt.
       - ../backend/fluksio:/app/backend/fluksio
+      # The worker speaks a protocol the engine version-matches, so mounting one
+      # without the other leaves a reloaded engine talking to the worker baked
+      # into the image — which is how every python node came to fail with
+      # "the worker answered request None" after a protocol change.
+      - ../worker/fluksio_worker:/app/worker/fluksio_worker
     environment:
       SMTP_HOST: "mailcatcher"
       SMTP_PORT: "1025"