Bundle kaya-otel in the Docker image

The tavolo-app otel extra was never installed: requirements.txt was
locked without it and the Dockerfile installs the local distributions
with --no-deps, so any container with OTEL_ENABLED set died at import
with "kaya-otel is not installed".

Add the extra's full closure (kaya-otel plus its OpenTelemetry/protobuf
dependencies) to the pinned lock and refresh the comments that claimed
the extra had to be added separately.

docker-compose.yml

@@ -123,7 +123,8 @@ services:
       CORS_EXPOSE_HEADERS: ${CORS_EXPOSE_HEADERS:-}
       CORS_MAX_AGE: ${CORS_MAX_AGE:-}
       # OpenTelemetry (kaya-otel): disabled unless OTEL_ENABLED is set.
-      # Requires the otel extra in the image (see server/pyproject.toml).
+      # The image bundles the otel extra (see packages/tavolo-app/pyproject.toml
+      # and server/requirements.txt).
       OTEL_ENABLED: ${OTEL_ENABLED:-}
       OTEL_SERVICE_NAME: ${OTEL_SERVICE_NAME:-}
       OTEL_EXPORTER_OTLP_ENDPOINT: ${OTEL_EXPORTER_OTLP_ENDPOINT:-}