Arch Vulkan Installation & Bottom Bar UI Update

This release fixes non-interactive Vulkan dependency installation on Arch-based systems and improves the bottom toolbar alignment and button sizing.

What’s New:

• Non-Interactive Arch Vulkan Install: Removed the interactive vulkan-devel group from the pacman install list.
• Concrete Vulkan Packages: Arch now installs base-devel, cmake, git, vulkan-headers, vulkan-icd-loader, shaderc, and spirv-headers with pacman -S --needed --noconfirm.
• Dependency Validation: Missing packages remain visible in the manager and the Install Missing button stays enabled until the selected backend is ready.
• Bottom Toolbar Layout: The language selector and tray preference stay grouped on the left, while a flexible spacer keeps the manager and About buttons on the right.
• Button Sizing: Manager/About buttons use natural minimum widths, compact padding, and vertical-center alignment to prevent unnecessary ellipsis and overlap.