[stable-33.0] fix(macOS): Force user to manually choose a local sync folder

[claucambra]

Summary

With the enabling of the sandbox in 33.x, we can no longer get access to the user's real home folder path without their explicit consent (i.e. the file picker and the ensuing permission granted by the system). The best way to fix this issue is to have the user explicitly choose where they wish to sync.

Checklist

• Sign-off message is added to all commits.
• The commit messages are following The Conventional Commits specification.
• The commit history is clean with no merge commits.
  • How to rebase your commits
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• Test(s) added to branch, with before/after results included in PR description, for performance improvements where applicable.
• Documentation has been updated or is not required.
• Backports requested where applicable (critical bugfixes).
• Labels added where applicable (bug/enhancement).
• Milestone added for target version.

AI (if applicable)

• The content of this PR was partly or fully generated using AI
  • I have read the guidelines for AI-assisted contributions.
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[github-actions]

Artifact containing the AppImage: nextcloud-appimage-pr-10745.zip

Digest: sha256:3df840c234e69d6d53c1588eebc2c8626753acefdd040d138258f4c2bd57ea3f

To test this change/fix you can download the above artifact file, unzip it, and run it.

Please make sure to quit your existing Nextcloud app and backup your data.

[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)
3 New Code Smells (required ≤ 0)

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[i2h3]

This is odd. That used to work with 33.0.0. This must be a regression. When this wizard step appeared, there was an automatic prompt for selecting a folder ever since. 😕 I know for sure because I implemented exactly that and made sure.