[WIP] Recover access to synchronization folder after app sandboxing

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Recover access to synchronization folder after</issue_title>
<issue_description>## Problem

• Clients before version 33.0.0 were not inside a macOS app sandbox. They worked with plain folder paths they could freely access in the local file system.
• The client release 33.0.0 introduced app sandboxing on macOS which requires users to explicitly approve access to folders outside the app sandbox.
• When a user has classic synchronization folder set up in a client installation below version 33.0.0 and then updates the client, the client suddenly cannot access the previously set up paths anymore.

Solution

• The client must acquire the bookmark data of security-scoped URLs created from the synchronization folder path(s). This can be achieved to make the user select the root folders in an open file panel once.
• When a synchronization root folder is missing its bookmark data, then a call to action needs to be presented on the synchronization folder in the settings which tells the user to select the folder in the file system in an open file panel.
• When the user-selected location does not match the previously set up root folder path, the selection should be ignored.

Remarks

• This is a release blocker.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Recover access to synchronization folder after #9480

---

🔒 GitHub Advanced Security automatically protects Copilot coding agent pull requests. You can protect all pull requests by enabling Advanced Security for your repositories. Learn more about Advanced Security.