Move the StatusToolbar out of GridContainer and into a new wrapper in MainContainer to fix the scrollbar overlap issue safely.

Plan:

1. MainContainer.mjs: Wrap GridContainer in a VBox Container (cls: ['neo-grid-wrapper']). Add StatusToolbar as a sibling.
2. GridContainer.mjs: Remove footerToolbar config.
3. Styling: Ensure the new wrapper picks up the Shadow/Radius styles from Viewport.scss.