Add theme manager with selectable themes and profiles:
- classic: Professional SOC-style dark theme (default)
- cards: Modern card-based UI with gradients
- cyberpunk: Neon glow effects with terminal aesthetics
Profiles extend themes with custom options:
- default, soc, modern, hacker
Theme selection available in Settings > Appearance with live preview.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
