refactor(auth): centralize role checks into utility

Removed direct user role string checks and replaced with type-safe utils.

app/middleware/auth.ts

@@ -20,19 +20,10 @@ export default defineNuxtRouteMiddleware(async (to) => {
   const requiredRole = to.meta.auth?.role
 
   if (requiredRole && auth.user.value) {
-    const userRole = auth.user.value.role.toUpperCase()
+    const userRole = auth.user.value.role
 
-    const roleLevels: Record<string, number> = {
-      'CITIZEN': 1,
-      'OPERATOR': 2,
-      'ADMIN': 3
-    }
-
-    const userLevel = roleLevels[userRole] || 0
-    const requiredLevel = roleLevels[requiredRole] || 0
-
-    if (userLevel < requiredLevel) {
-      console.warn(`[Auth] User role ${userRole} (level ${userLevel}) insufficient for required ${requiredRole} (level ${requiredLevel})`)
+    if (!hasMinimumRole(userRole, requiredRole)) {
+      console.warn(`[Auth] User role ${userRole} insufficient for required ${requiredRole}`)
       return navigateTo('/')
     }
   }