Summary

Fix light mode resetting to dark when navigating between builder sections
(Design, CMS, etc.). The DarkModeProvider was unconditionally forcing dark
mode on every pathname change within /ycode, ignoring the user's saved
theme preference.

Changes

• Update DarkModeProvider to check localStorage theme preference before applying dark mode on builder routes
• Use light/dark-aware text color for the save status indicator (Ready/Saving/Saved) in HeaderBar

Test plan

• Select Light theme in the builder menu
• Navigate between Design, CMS, and Settings — theme should stay light
• Verify the save status text is visible in both light and dark modes
• Select System theme and verify it follows OS preference across navigation
• Refresh the page — theme should persist from localStorage