fix(auth) : use dedicated plainPassword field for password hashing

- Add non-persisted plainPassword field to User entity (write-only via API)
- Remove direct write access to password field
- Update UserPasswordHasherProcessor to hash from plainPassword
- Update frontend DTO and UserDrawer component

Ticket: T-009

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/components/user/UserDrawer.vue

@@ -1,5 +1,5 @@
 <template>
-    <AppDrawer v-model="isOpen" :title="isEditing ? 'Modifier un utilisateur' : 'Ajouter un utilisateur'">
+    <AppDrawer v-model="isOpen" :title="isEditing ? $t('users.editUser') : $t('users.addUser')">
         <form class="flex flex-col gap-2" @submit.prevent="handleSubmit">
             <MalioInputText
                 v-model="form.username"
@@ -90,6 +90,8 @@ import { useProjectService } from '~/services/projects'
 import type { Client } from '~/services/dto/client'
 import type { Project } from '~/services/dto/project'
 
+const { t } = useI18n()
+
 const props = defineProps<{
     modelValue: boolean
     item: UserData | null
@@ -114,7 +116,7 @@ const clients = ref<Client[]>([])
 const allProjects = ref<Project[]>([])
 
 const clientOptions = computed(() => [
-    { label: 'Aucun client', value: null as number | null },
+    { label: t('common.noClient'), value: null as number | null },
     ...clients.value.map((c) => ({ label: c.name, value: c.id as number | null })),
 ])
 
@@ -190,7 +192,7 @@ async function handleSubmit() {
             allowedProjects: form.allowedProjectIds.map((id) => `/api/projects/${id}`),
         }
         if (form.password) {
-            payload.password = form.password
+            payload.plainPassword = form.password
         }
 
         if (isEditing.value && props.item) {