Retrieve git issue #111, create local feature branch, implement the changes, then commit and push changes to origin, then raise PR for Traktion

Issue Title: Add get and list files support to public archive REST API
Issue Number: 111

Description:
As a software engineer
I want to provide a GET endpoint for public archive via REST API
So that I can list files in an archive

Given both POST and PUT to /anttp-0/multipart/public_archive are already supported
When listing files in an archive sub-directory
Then add a GET /anttp-0/public_archive/{address}/{*path} endpoint in /src/lib.rs that calls get_public_archive function in public_archive_controller.rs
And let {*path} represent the directory or file within the archive to be retrieved

Given a {*path} can be a directory or a file
When the path is a file
Then return the content as a JSON document containing a content field, with a base64 encoded version of the content
And see get_chunk function in chunk_controller.rs as an example of base64 content
And see example JSON below

Given a {*path} can be a directory or a file
When the path is a directory
Then return the content as a JSON document containing a files field, with a list of the files in that directory
And see example JSON below

Implementation Notes

- Place any unit tests at the bottom of the same file as the associated production code
- Increment patch version of anttp package in Cargo.toml
- Create a copy of this issue description and save to /spec using the name of this issue as the filename (with lower underscore case, starting with the 5 char padded issue number, e.g. 00001_issue_title.txt)
- Integrate support with MCP tools and gRPC if necessary
- Do not attempt to clone or mock other *_service.rs code
- Mock PublicArchiveCachingClient using mockall : 

Example JSON response for file URL at path '/anttp-0/public_archive/{address}/path/to/file.txt':

```json
{
  "files": [],
  "content": "ZmlsZS50eHQgY29udGVudA==",
  "address": "{address}"
}
```

Example JSON responses for directory URL at path '/anttp-0/public_archive/{address}/path/to/directory/':

```json
{
  "files": [
    "file.txt",
    "file2.txt"
  ],
  "content": "",
  "address": "{address}"
}
```
