Add Vertical HD (1080x1920) Safe Area Grid Option

I’d like to propose adding a Vertical HD (1080x1920) safe area option to the grid feature in Shotcut. This would be helpful when editing FHD (1920x1080) videos, allowing us to see how they look in vertical HD without needing to add a Reframe filter.

The goal is to provide a way to preview the vertical HD area while editing, not to export FHD to vertical HD. If accepted, I’d suggest including two types of Vertical HD safe area grids:

  1. A standard Vertical HD grid
  2. A grid with additional lines indicating areas where buttons (e.g., follow, subscribe) typically appear, helping us avoid placing text or important content in those areas.

This feature would complement the existing Safe Area grid and help streamline the editing process.