Add background dimming behind major interface windows

[Branikolog]

When a castle, battle, or other large interface window is opened, the visible Adventure Map around it can be distracting, especially for new players. The presence of Adventure Map UI elements also creates an expectation that they remain active and continuously updated. For example, resource counters visible around the window are often refreshed only after the current screen is closed, which some players perceive as a bug.

A subtle darkening effect around the active window could help visually separate interface layers and make it clearer which part of the UI currently has focus. Since these windows already use a shadow effect, the darkening intensity could be similar to that shadow and therefore remain consistent with the existing visual style.

This could be particularly beneficial on low-height resolutions (such as x480), including mobile devices, where the top and bottom parts of the decorative frame are often outside the visible area. In such cases, only the left and right borders remain visible, making the frame look incomplete.

A darkened background would provide a cleaner visual separation and could even allow removing the partially visible frame entirely on x480 layouts, while preserving the full decorative frame on higher resolutions where it is displayed correctly.