Fix start screen colors in light mode

[Xuyiyang23333]

Summary

• replace hard-coded white foreground styles on the start screen with SwiftUI semantic colors
• make the device and resolution pills, start button, and utility buttons adapt to the active appearance
• keep fixed white styling for playback controls and video overlays, where the content remains on a dark or video background

Problem

The start screen's material and Liquid Glass appearance adapt between light and dark mode, but its foreground colors were hard-coded to white. In light mode this produced low-contrast text and controls on the lighter panel.

Using .primary, .secondary, and Color.primary.opacity(...) allows the foreground and control chrome to follow the system appearance together with the panel.

Validation

• xcodebuild -project Consolation.xcodeproj -scheme Consolation -configuration Release -destination 'platform=macOS' ... build (BUILD SUCCEEDED)
• git diff --check
• manually verified the generated macOS app in both light and dark mode