using docker volume results in permissions denied

```
docker volume create tezos_node
docker run -v tezos_node:/var/run/tezos ....
...
Error: Unix permission denied
```
This is because the volume is mounted at the path, owned by 'root' which the tezos user cannot modify.

I was able to fix this by modifying the Dockerfile as follows:

```
RUN useradd -ms /bin/bash tezos

RUN mkdir -p /var/run/tezos/node /var/run/tezos/client && \
chown tezos /var/run/tezos/node /var/run/tezos/client
```

Start with the repository's Dockerfile and reproduce the documented docker volume create and docker run commands. Verify that the mounted /var/run/tezos paths are writable by the tezos user, and use the reported Unix permission-denied error to confirm the issue is resolved.

Written by the indexing model from the issue text.