feat: Migrate from CoreUI/Bootstrap to Material UI (MUI)

[devin-ai-integration]

Summary

This PR completely replaces the CoreUI/Bootstrap design library with Material UI (MUI) throughout the admin template. The migration includes:

• Dependencies: Removed @coreui/* packages and added @mui/material, @mui/icons-material, @emotion/react, @emotion/styled, and react-chartjs-2
• Theme System: New src/theme.js with MUI ThemeProvider supporting light/dark mode via Redux
• Layout Components: Migrated AppHeader (AppBar), AppSidebar (Drawer), AppFooter, AppContent, and DefaultLayout
• Navigation: Restructured _nav.js to use a data-driven approach with type field instead of CoreUI components
• All View Components: Migrated 40+ component demo pages (base, buttons, forms, notifications, charts, icons, widgets)
• Pages: Migrated Login, Register, Page404, Page500, and Dashboard
• Charts: Switched from @coreui/react-chartjs to react-chartjs-2 with Chart.js

Review & Testing Checklist for Human

This is a high-risk PR due to the scope of changes. Please verify:

• Visual inspection: Run npm start and verify all pages render correctly - the build passes but no visual testing was performed
• Theme switching: Test light/dark mode toggle in the header works and persists
• Sidebar navigation: Verify all nav items work, groups expand/collapse, and active states display correctly
• Responsive behavior: Test sidebar collapse on mobile and layout adjustments at different breakpoints
• Dashboard charts: Verify MainChart and widget charts render with correct colors and data

Recommended test plan:

1. Run npm start and navigate through all sidebar menu items
2. Toggle theme between light and dark mode
3. Test on mobile viewport to verify responsive sidebar
4. Check Login/Register/404/500 pages render correctly
5. Verify form components (inputs, selects, checkboxes) are functional

Notes

• Some CoreUI PRO features (Calendar, Smart Table, Virtual Scroller links) were removed from navigation as they were external links
• MainChart now uses static data instead of random values to fix a React purity lint error
• SCSS files were significantly simplified since MUI handles styling via its own system

Link to Devin run: https://partner-workshops.devinenterprise.com/sessions/d365159100db4b68bef360a49d634ff9
Requested by: hemaladha.k@cognizant.com

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring