Allow selecting multiple workflows at once in the Request Approval modal (checkboxes instead of single selection) #450

When requesting approval on a file or folder, the modal currently allows selecting only one workflow at a time (radio-button style).
In many real-world use cases (e.g. contract review), a document needs parallel opinions from several departments (Legal, Technical, Accounting, HR, etc.). Currently the user has to open the Request Approval dialog multiple times and select one workflow after another. This is cumbersome and error-prone.

Please change the Request Approval modal so that users can select multiple workflows at once using checkboxes. After confirming, all selected workflows should be started in parallel on the same file/folder.