I incorrectly removed next-themes thinking it caused the hydration
warning. The actual mismatch was a `__gcrremoteframetoken` attribute
added to <html> by a browser extension, which the previous commit
already addressed via `suppressHydrationWarning`.
Restored:
- ThemeProvider wrap in the layout
- ThemeToggle component
- Sonner Toaster's useTheme() so toasts respect the chosen theme
- Appearance card on the Settings page
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
yiekheng
e6f4e3b2e5