feat(permissions) : add role-based UI guards and readonly mode for viewers

- Add usePermissions composable (isAdmin, canEdit, canView)
- Password-protected profile login with modal on profiles page
- Disable all form fields for ROLE_VIEWER across edit/create pages
- Show navigation buttons (Modifier/Consulter) for all roles, hide delete for viewers
- Add readonly prop to ModelTypeForm for category pages
- Disable modal fields (sites, constructeurs) for viewers
- Guard /admin routes in middleware

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/components/machine/MachineDetailHeader.vue

@@ -60,6 +60,8 @@ import IconLucideSquarePen from '~icons/lucide/square-pen'
 import IconLucideEye from '~icons/lucide/eye'
 import IconLucidePrinter from '~icons/lucide/printer'
 
+const { canEdit } = usePermissions()
+
 defineProps<{
   title: string
   isDetailsView: boolean