- Add `--text-on-accent` CSS variable (white) for text on accent backgrounds
- Replace hardcoded `var(--bg-primary)` with `--text-on-accent` across components
- Update dark theme surface, border, and text color tokens for better contrast
- Adjust dark mode surface colors (`#1F1D1C` → `#242221`) for improved depth
- Refine border and text-muted colors for better visual hierarchy
Signed-off-by: 诺墨 <normal@normalcoder.com>