Improved modal responsiveness on small screens

Dialogs now adapt to the viewport height and scroll consistently as a single block, preventing footer buttons from being cut off on shorter screens.

Modal dialogs across the application now clamp to the visible viewport height and scroll as a single block when the content exceeds the available space. Previously, on shorter screens or smaller browser windows, action buttons such as Generate, Upload, or Save could be hidden beneath the fold or cut off entirely. The Configure Photo Shoot, Your Photos uploader, and Create Packshot dialogs were the most affected and have been updated to use the new layout, alongside related dialogs in the content generation flows.