Remove button behaviour

**Describe the bug in current situation**
Currently the remove button in the edit state is always active and it should only show when the user is adding a new SI or editing an SI that has not been submitted yet. Active SIs that have already been submitted should not be seeing the remove button.

**Expected behaviour:**

Users adding new SI or editing SI that has not be entered in registry yet

Users editing SI already in registry

If user selects remove then we need to have a pop up dialogue to confirm removal before removing: https://www.figma.com/design/4oi1IWHe0DmbY8EZk3Srs3/Add%2Fedit-SI?node-id=2757-21568&t=AYPKneIigyodJpVQ-1

**Impact of this bug**
Users are currently being allowed to remove an SI when editing an SI who is already filed in the registry. The only way a user can remove an SI is on initial entry or edit before SIs have been submitted to the registry. Otherwise the only option to remove is to cease and then delete if the SI is already filed.

Start by tracing the frontend add/edit SI screen described in the issue and compare the two provided screenshots with the linked Figma design. Verify the remove button is limited to new or unsubmitted SIs, and that selecting it shows a confirmation dialog before removal; check both submitted and unsubmitted states.

Written by the indexing model from the issue text.