Desktop,Mobile,Cli: Fixes #13522: Fix "cannot add an item as a child of a read-only item" error when updating share IDs

[personalizedrefrigerator]

Summary

This pull request fixes an error related to read-only shares by disabling a "not read-only" assertion when updating share_ids (e.g. if the share_ids were invalid due to an incomplete sync or issue elsewhere). Previously, if one share_id failed to update, calls to updateAllShareIds could fail. This prevented sharing new notebooks.

Fixes #13522.

Testing

This pull request includes an automated test that failed previously.

I have verified that:

• It's possible to share a notebook without the "read-only share" error in my test environment.

[personalizedrefrigerator]

Note: This may lead to conflicts:

joplin/readme/dev/spec/read_only.md

Line 24 in 94725c5

- If a local read-only item has been modified, and the synchroniser tries to upload it, Joplin Cloud responds with a read-only error. The synchroniser local item is copied to the conflict folder and the remote item overwrites the local one.