fix: improve text contrast for selected dropdown items in dark mode

When dropdown items are selected in dark mode, the text now uses
lighter brand colors for better contrast against gray.700 background:

Dark mode selected:
- Primary text: brand.700 → brand.200 (light blue)
- Secondary text: brand.600 → brand.300 (light blue)

Light mode selected:
- Primary text: brand.700 (unchanged)
- Secondary text: brand.600 (unchanged)

This ensures selected items remain clearly readable in both themes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/web/src/app/create/worksheets/addition/components/OrientationPanel.tsx

@@ -396,7 +396,13 @@ export function OrientationPanel({
                               className={css({
                                 fontSize: 'sm',
                                 fontWeight: 'semibold',
-                                color: isSelected ? 'brand.700' : isDark ? 'gray.200' : 'gray.700',
+                                color: isSelected
+                                  ? isDark
+                                    ? 'brand.200'
+                                    : 'brand.700'
+                                  : isDark
+                                    ? 'gray.200'
+                                    : 'gray.700',
                               })}
                             >
                               {count} problems
@@ -404,7 +410,13 @@ export function OrientationPanel({
                             <div
                               className={css({
                                 fontSize: 'xs',
-                                color: isSelected ? 'brand.600' : isDark ? 'gray.400' : 'gray.500',
+                                color: isSelected
+                                  ? isDark
+                                    ? 'brand.300'
+                                    : 'brand.600'
+                                  : isDark
+                                    ? 'gray.400'
+                                    : 'gray.500',
                               })}
                             >
                               {itemCols} cols × {rows} rows