Are cooked foods that contain milk potentially dangerous, or will significant heating inactivate any contaminating harmful viruses?

We would love to be able to tell you that any cooked food is perfectly safe but that cannot be guaranteed. There will be some reduction in ability to infect a person ingesting cooked food compared to ingesting the same amount of plain milk, but it cannot be guaranteed to be virus-free. There is certainly a lower level of danger from milk being, in most cases, one of many ingredients in prepared foods compared to drinking large quantities of milk directly as a beverage.