Provide better UI feedback about cards that can't be dragged or edited
Depends on D20273. Fixes T10722. Currently, we don't make it very clear when a card can't be edited. Long ago, some code made a weak attempt to do this (by hiding the "grip" on the card), but later UI changes hid the "grip" unconditionally so that mooted things.
- Replace the edit pencil with a red lock.
- Provide cursor hints for grabbable / not grabbable.
- Don't let users pick up cards they can't edit.
Test Plan: On a workboard with a mixture of editable and not-editable cards, hovered over the different cards and was able to figure out which ones I could drag or not drag pretty easily. Picked up cards I could pick up, wasn't able to drag cards I can't edit.
Reviewed By: amckinley
Maniphest Tasks: T10722
Differential Revision: https://secure.phabricator.com/D20274