Allow to lock items when date is synched with integration

Currently when Epics, Features and Requirements use a Date Sync with our DevOps it would make sense to be able to lock the dates in UI and Bar-Lenght handles as they are exclusively coming from the external system. This would avoid:

• A contributor accidentally dragging a bar's lenght to change a date, which could then accidentally back-sync.

• The date field to become a "imaginary wishlist" how long feature implementation should take, as the team itself is providing those dates.

• Prevent confusion when the sync is 1-way and shouldn't be changed thereafter.