Upgrade MUI 6 to 7 (devDependency)

[smartlabsAT]

Description

MUI v7 is available. This is a devDependency used in Storybook stories.

Packages to update

• @mui/material: ^6.4.3 -> 7.3.9

Breaking Changes to investigate

• Component API changes
• Theme structure changes
• Import path changes

Tasks

• Read MUI v7 migration guide
• Update @mui/material
• Fix Storybook story imports if needed
• Verify stories render correctly