Remove unused react-beautiful-dnd dependency

[gdiab]

Problem

react-beautiful-dnd and @types/react-beautiful-dnd are still in package.json but are no longer used anywhere in the codebase. The project migrated to @dnd-kit for all drag-and-drop functionality.

Proposed Solution

npm uninstall react-beautiful-dnd @types/react-beautiful-dnd

Acceptance Criteria

• Both packages removed from package.json
• npm run build still succeeds
• No remaining imports of react-beautiful-dnd in the codebase