UI: Use DragFloat3 for Camera Offset controls

[chrisraff]

The Camera Offset sliders under Camera Freeze use SliderFloat3 with a +- 4000 range,
which makes dialing in precise position values impractical - the slider moves too
coarsely to land on a specific value.

This replaces them with DragFloat3, which:

• Defaults to a slow drag speed (0.5 units/px) suitable for fine positioning
• Supports Shift+drag for faster coarse adjustment
• Supports Alt+drag for extra fine adjustment
• Supports Ctrl+Click or Double Click to type a value directly
• Retains the +- 4000 range

A tooltip is added to the control to surface these shortcuts for users who may not
be familiar with ImGui drag inputs.

Initial implementation by GitHub Copilot.

[mrbelowski]

change looks fine to me. Is it worth looking for other instances in the UI where the sensitivity & resolution of the sliders could be improved?

No idea why the PR build fails

[chrisraff]

I just ran through the UI, the only other slider I found where this seems like an issue to me would be "input > controller pitch offset" since its range is +- 90 and very precise changes could be valuable. However, it's already quite a large slider.

Lmk if I should do that change or you want anything else before accepting the PR