VSN-2500: Migrate flottes forms, anomaly detection table, and vehicle planning to shadcn

Summary

• Fiche Véhicule & Marque/Modèle forms — migrated from MUI Grid/Typography to shadcn FormContainer, FormField, ActionButtons with purple-tinted cards (#EDE9FB), colored left borders, and Lucide icons
• Anomaly detection table (/dashboard/flottes/vehicule/kilometrage) — replaced MUI TableManager with CSS grid table, shadcn TableHeadCustom/TablePagination, purple info card, and dark pill tab labels
• Vehicle planning full redesign (/dashboard/flottes/vehicule/planning) — complete migration matching chauffeur planning design:
  • Dark purple header with "Véhicules" label and hour/minute tick marks
  • Colored vehicle rows with avatars, accent borders, and hover popover with vehicle details
  • Skeleton shimmer loading animation on initial load
  • Migrated toolbar, event details drawer, add intervention dialog, intervention table sidebar to shadcn/Tailwind
  • Redesigned intervention details popover (clean white card with icon rows)
  • Intervention list table migrated to CSS grid with neo-shadow rows
  • Default zoom set to 75%
  • Zoom label with search icon added to schedule toolbar
• Usager search bar — made full-width in circuit usager selector

Closes VSN-2500