fix(shell_integration): use title case for macOS and Linux context menus

[cbrnr]

Resolves

#10525

Summary

This seemingly simple change turned out to be a bit more involved. I don't know if my proposed solution is the best one, as it involves the explicit mapping of the corresponding context menu entries from sentence case to title case multiple times (once for each integration).

I have also not tested the changes in the UI, as I was hoping that the builds will be available from CI, which would be much easier for testing.

TODO

• Add unit tests?

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
  • 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.

[Rello]

duplicate of #10581 ?

[cbrnr]

Didn't see that, looks like it!