Fix changelog colors for dark mode

Changelog UI now follows your theme — Replaced hardcoded colors with semantic tokens so the public changelog respects light, dark, and system theme preferences.

Replaced hardcoded colors (e.g. bg-white, border-black, border-black/10) across the public changelog with semantic tokens (bg-background, border-border, border-foreground). This fixed contrast and legibility issues in dark mode and ensured the ThemeProvider's system/dark/light preference is correctly applied.frontend