fix(download): allow nested file paths in download route

[djhavert]

Description

This PR updates the /download route to support nested directory structures. Previously, the route used a single parameter match (/:file_path), which caused Express to return a 404 "Not Found" error whenever a file within a sub-folder (e.g., /46d61d754c2ebde3fd90a4d653b560e4/file01.txt) was requested.

The route now uses a wildcard parameter to capture the full path following the /download/ prefix, ensuring compatibility with complex file structures stored on external mounts.

Changes Made

List the main changes made in this PR. Be as specific as possible.

• Feature added
• Bug fixed
• Code refactored
• Tests changed
• Documentation updated
• Other changes: [describe]

Checklist

Before submitting this PR, please make sure that:

• Your code passes linting and coding style checks.
• Documentation has been updated to reflect the changes.
• You have reviewed your own code and resolved any merge conflicts.
• You have requested a review from at least one team member.
• Any relevant issue(s) have been linked to this PR.