refactor: clean up dead files, restructure nav, align QuickStartPage to monochrome
- Delete 6 unused files: ThemeToggle, themeStore, AppLayout-original,
QuickStartPage-Enhanced, UpgradePrompt, SettingsPage
- Restructure Account/Settings navigation: merge Settings into Account page,
make AccountSettingsPage the /account index, remove orphaned /account-settings route
- Remove "Settings" nav item (consolidated under Account)
- Add export preferences and team categories link to AccountSettingsPage
- Align QuickStartPage to monochrome design system: replace cyan/blue/violet
accent colors with white opacity variants
- Replace non-functional search button with search spinner indicator
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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