feat(theme): align UI color scheme with app icon

[owieth]

Summary

The current app UI uses a blue-navy background with a cyan primary accent, which doesn't match the app icon's aesthetic. The icon features a near-black background with a gold → amber → orange → deep-red arc gradient. This issue tracks updating the theme to align the UI with the icon's warm, dark palette.

Proposed Changes

• Backgrounds: Remove blue tint from backgroundDark and backgroundNavy; shift to near-black with a subtle warm tint
• Primary accent (accentCyan token): Change from cyan (0.0, 0.8, 0.9) to amber/gold (0.82, 0.52, 0.08) — matching the icon's gauge start color
• Critical red (criticalRed token): Change from Color.red to the icon's deep warm red (0.78, 0.12, 0.06)
• Status bar gradient: Update from cyan → purple → red to gold → amber → deep-red
• CPU ring gauge (RingGradients.cpu): Arc from gold to deep-red, mirroring the icon's circular gauge

Files

• MacVitals/Theme/Theme.swift — color tokens + gradients
• MacVitals/Views/Components/RingGaugeView.swift — RingGradients.cpu

All 19 view files auto-inherit the changes since they reference Theme.Colors.* tokens.

🤖 Generated with Claude Code