Fix CSS compilation by adding missing styles and variables

## Critical CSS Fixes
- ✅ Added missing index page styles (_index.scss) for main application
- ✅ Restored original CSS variables and color scheme compatibility
- ✅ Added comprehensive reports-table styles with proper cell formatting
- ✅ Fixed theme variables to match original design (updated colors)
- ✅ Added missing form, button, and layout components

## Enhanced Styles
- ✅ Proper table cell styling (.location-cell, .details-cell, .time-cell, .remaining-cell)
- ✅ Status indicators for urgent/warning/normal time remaining
- ✅ Enhanced responsive design for mobile tables
- ✅ Form and input styling consistency
- ✅ Theme toggle and header components
- ✅ Error/success message styling

## Architecture Improvements
- ✅ Modular imports: admin styles + index styles + shared components
- ✅ Better CSS variable organization with light/dark theme support
- ✅ Maintained backward compatibility with existing classes
- ✅ Compressed CSS output for production performance

The application now has full styling coverage with the new SCSS architecture.