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/composables/useAdminProfiles.ts

@@ -0,0 +1,80 @@
+import { ref } from 'vue'
+import { useApi } from './useApi'
+
+export interface AdminProfile {
+  id: string
+  firstName: string
+  lastName: string
+  email: string | null
+  isActive: boolean
+  hasPassword: boolean
+  roles: string[]
+  createdAt: string
+  updatedAt: string
+}
+
+export function useAdminProfiles() {
+  const { get, post, put } = useApi()
+  const profiles = ref<AdminProfile[]>([])
+  const loading = ref(false)
+
+  const fetchAll = async () => {
+    loading.value = true
+    try {
+      const result = await get<AdminProfile[]>('/admin/profiles')
+      if (result.success && result.data) {
+        profiles.value = result.data
+      }
+    } finally {
+      loading.value = false
+    }
+  }
+
+  const createProfile = async (data: {
+    firstName: string
+    lastName: string
+    email?: string
+    password?: string
+    role?: string
+  }) => {
+    const result = await post<AdminProfile>('/admin/profiles', data)
+    if (result.success) {
+      await fetchAll()
+    }
+    return result
+  }
+
+  const updateRole = async (id: string, role: string) => {
+    const result = await put<AdminProfile>(`/admin/profiles/${id}/role`, { role })
+    if (result.success) {
+      await fetchAll()
+    }
+    return result
+  }
+
+  const setPassword = async (id: string, password: string) => {
+    const result = await put<AdminProfile>(`/admin/profiles/${id}/password`, { password })
+    if (result.success) {
+      await fetchAll()
+    }
+    return result
+  }
+
+  const deactivateProfile = async (id: string) => {
+    const result = await put<AdminProfile>(`/admin/profiles/${id}/deactivate`, {})
+    if (result.success) {
+      await fetchAll()
+    }
+    return result
+  }
+
+  return {
+    profiles,
+    loading,
+    fetchAll,
+    createProfile,
+    updateRole,
+    setPassword,
+    deactivateProfile,
+  }
+}