Fix exec format error in pylsp Docker container

## Problem
The pylsp Docker container fails to start with an exec format error:
```
exec /usr/src/app/run_pylsp.sh: exec format error
```

This occurs because the `python:3.10-slim` base image may not include bash by default, causing the bash script to fail execution.

## Solution
- Explicitly install bash in the container
- Update ENTRYPOINT to use `/usr/bin/env bash` for proper script execution