Juno docker build fails on windows machines

## Summary

The Docker build can fail on Windows checkouts because the helper shell scripts under `docker/` are checked out with CRLF line endings.

For example, `docker/get_grpc_probe.sh` is copied successfully into the Alpine image, but executing it fails with a misleading error like:

```text
/bin/sh: get_grpc_probe.sh: not found
```

The script itself exists and its contents are valid. The issue is that the shebang is checked out as:

```text
#!/bin/sh\r\n
```

so Linux effectively attempts to use `/bin/sh\r` as the interpreter.

## Reproduction

On a Windows checkout with:

```text
core.autocrlf=true
```

both of the following scripts contain CRLF line endings:

```text
docker/get_grpc_probe.sh
docker/get_protoc.sh
```

This can be confirmed by inspecting the file bytes or checking for carriage returns.

## Proposed fix

Add a `.gitattributes` file to the Juno repository that explicitly requires Unix line endings for shell scripts and Dockerfiles, for example:

```gitattributes
* text=auto

*.sh text eol=lf
Dockerfile text eol=lf
*.dockerfile text eol=lf
```

Then renormalize the existing tracked files:

```bash
git add --renormalize .
```

and commit the resulting changes.

This would ensure that shell scripts are checked out with LF line endings even on Windows systems where `core.autocrlf=true`.

Optionally, CI could also include a check that rejects CRLF line endings in executable shell scripts to prevent regressions.

## Why this is preferable

Normalizing the files manually fixes an individual checkout, but the issue can recur for any developer cloning the repository on Windows. Enforcing the line endings through `.gitattributes` makes the requirement part of the repository itself and avoids relying on developers' local Git configuration.

Inspect docker/get_grpc_probe.sh and docker/get_protoc.sh, then reproduce the checkout with core.autocrlf=true and verify their line endings. Add the repository line-ending rules described in the issue, renormalize tracked files, and confirm the Docker build no longer fails when the scripts are executed from a Windows checkout.

Written by the indexing model from the issue text.