fix(macOS): Verify ability to access Local Network

[claucambra]

Resolves

#10452

Summary

On macOS 15+ it is possible for users to choose to disable access to the local network to the desktop client. This means if a user tries to connect to a server instance on the same network, the connection will fail if local network access is not granted.

As it stands, it is impossible for the code to differentiate between a "legitimate" connection failure and one caused by a connection denied by the system. This can make it confusing for users to understand why the application is failing to connect to an instance.

This PR adds a check for local network access permissions on macOS (and includes a polymorphic interface that can be used to implement a similar feature if/when Windows and Linux desktops choose to implement such an access restriction like macOS, iOS/iPadOS and Android have).

/backport to stable-34.0 please

Checklist

• Sign-off message is added to all commits.
• The commit history is clean with no merge commits.
  • How to rebase your commits
  • How to squash commits with rebase
• Uploaded screenshots from before and after for UI changes.
• 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.
  • I have read Nextcloud's AI Contribution Policy.

[claucambra]

/backport to stable-34.0 please

[sonarqubecloud]

Quality Gate failed

Failed conditions
1 Security Hotspot
70.0% Coverage on New Code (required ≥ 80%)
E Maintainability Rating on New Code (required ≥ A)
128 New Code Smells (required ≤ 0)

See analysis details on SonarQube Cloud

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[github-actions]

Artifact containing the AppImage: nextcloud-appimage-pr-10460.zip

Digest: sha256:9b6c22fbcf5df13969bd9322943235869e2cb655a807a69cb50fcdc7b4b08202

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.

[Rello]

nice one!

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[github-actions]

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