refactor(flottes): migrate Fournisseur, Révision, Réparation, Sinistre fiches to shadcn
Summary
- Migrate Fiche Fournisseur to shadcn FormField/FormContainer/ActionButtons with purple section card and Truck icon
- Migrate Fiche Révision to shadcn with purple card, Wrench icon, and Tailwind status alert replacing MUI Alert
- Migrate Fiche Réparation to purple card with Wrench icon, orange alert for closed repairs, 2-column grid layout
- Migrate Fiche Sinistre to 3 progressive purple section cards (Informations, Description, Suivi administratif) with Car/FileText/ClipboardList icons
- Replace MUI Grid/Box/Typography/Alert with Tailwind classes across all 4 fiches
Closes VSN-2503