Remplacement de Tailwind CSS par Material-UI pour un design plus professionnel.

1. Installation MUI:
   - @mui/material @mui/icons-material
   - @emotion/react @emotion/styled (styling engine)

2. Configuration theme (theme.ts):
   - Palette couleurs (primary=bleu, secondary=violet)
   - Typography (Roboto font family)
   - Components overrides (buttons, cards)
   - Border radius 8px

3. Main.tsx:
   - ThemeProvider wrapping App
   - CssBaseline pour reset CSS Material

4. Dashboard refactorise (100% MUI):
   - AppBar + Toolbar (header professionnel)
   - Container responsive (maxWidth xl)
   - Paper elevation pour cartes (ombres)
   - Typography pour textes (h6, caption, body2)
   - Alert avec IconButton pour erreurs
   - Stack + Box pour layout flexbox
   - Icons: ScienceIcon, CloseIcon

Avantages MUI:
- Design Material cohérent et professionnel
- Composants accessibles (ARIA)
- Animations fluides
- Theme customizable
- TypeScript support excellent
- Document...

Initialize Turborepo monorepo with Python backend and React frontend

- Setup Turborepo configuration with workspaces
- Configure Python FastAPI backend
  - Create project structure (core, analytics, api, models)
  - Add requirements.txt with FastAPI, Uvicorn, Pydantic, etc.
  - Basic FastAPI app with health endpoints
  - CORS middleware for frontend integration
- Configure React + TypeScript + Vite frontend
  - Install dependencies (Chart.js, D3.js, Zustand, Axios)
  - Setup Tailwind CSS with PostCSS
  - Create component directory structure
  - Basic landing page with Tailwind styling
- Add comprehensive README files
- Configure .gitignore for Python and Node.js

Phase 1 Complete ✓
Next: Phase 2 - Core simulation engine implementation