CLI: Use the new DELETE project endpoint

See the description for https://app.clickup.com/t/861nayppe and https://app.clickup.com/t/861nayqwz and mimic the same in the py-client/plugin.

The existing remove CLI function:

• should use the POST v2/project/{id}/scheduleDelete by default and returns when the project will be deleted
• should have a new flag -f, --force-delete to remove the project immediately by calling DELETE /project/{id}

Also, add a help text to that CLI function explaining that normal remove will schedule the project for deletion and the force will remove it forever immediately.

In autotests, use the new version (immediate delete) when doing cleanup.

Comments
Martin D: immediate removal of projects added to python API: https://github.com/MerginMaps/mergin-py-client/pull/177
Martin D: For the time being, clients still use the "old" v1 delete endpoint - we should switch to the v2 delete endpoint only after some time when also CE/EE servers are likely to be migrated already...

Migrated from: https://app.clickup.com/t/861nayu2h

Beginne mit der vorhandenen remove CLI-Funktion in py-client/plugin und den autotests, die Projekte bereinigen. Vergleiche ihre aktuelle Löschanfrage mit den v2 scheduleDelete- und sofortigen DELETE-Endpunkten und überprüfe anschließend den Hilfetext, die force-delete-Option, die zurückgegebenen Planungsinformationen und das Bereinigungsverhalten anhand der relevanten Tests.