Replace recording batch download powershell script with web file-system apis

[hudson-newey]

A common problem for users is that batch downloading audio requires the use of a Powershell script.

This leads to problems such as

• The incorrect powershell version being installed
• The user and/or powershell script might not have execute permissions
• Troubles in the shell (eg. navigating to the directory)

Replacing this with file system apis will allow the user to select a directory to batch download audio recordings to (reducing technical friction with powershell).

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User flow:

1. showDirectoryPicker() dialog for the user to select a directory
2. getDirectoryHandle(, {create: true}) to make sub directories for the sites (ensure that this doesn't generate additional pop-ups)
3. check if each file exists
4. write the streams from browser fetch

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Potentially using the following file-system apis:

• getFileHandle
• FileSystemDirectoryHandle
• getDirectoryHandle