Refactor ProjectLayout and ProjectSidebar to implement a toggleable sidebar...

Refactor ProjectLayout and ProjectSidebar to implement a toggleable sidebar feature. Update sidebar context for expanded/collapsed states and enhance scrollbar styling for better user experience across light and dark modes.

重构 ProjectLayout 和 ProjectSidebar 以实现可切换的侧边栏功能。更新侧边栏上下文以支持展开/折叠状态，并增强滚动条样式，以改善光明和黑暗模式下的用户体验。