feat(project-management) : extract Projects/Tasks front into Nuxt module layer

Tranche 4 of LST-65. Companion to the backend module migration.

- Move pages (my-tasks, projects, projects/[id]/{index,groups,archives}),
  18 components (project + task), 10 services and 10 DTOs into
  frontend/modules/project-management/ (auto-detected layer).
- Rewrite explicit ~/services/* and ~/services/dto/* imports across 38
  consumers (admin tabs, mail modals, dashboard, mail page, layout) including
  the time-tracking module whose DTOs referenced project/task/task-tag.
- clients.ts and shared DTOs (client, user-data) stay at the root.
- Routes /my-tasks, /projects, /projects/:id(/groups|/archives) preserved;
  i18n stays global.

nuxt build passes; routes confirmed.

frontend/modules/project-management/components/ProjectGroupTab.vue

@@ -0,0 +1,169 @@
+<template>
+    <div>
+        <div class="flex items-center justify-between">
+            <h2 class="text-lg font-bold text-neutral-900">Groupes</h2>
+            <div class="flex items-center gap-3">
+                <MalioButton
+                    variant="tertiary"
+                    button-class="w-auto px-3"
+                    :label="showArchived ? $t('archive.hideArchived') : $t('archive.showArchived')"
+                    @click="showArchived = !showArchived"
+                />
+                <MalioButton
+                    v-if="!showArchived"
+                    icon-name="mdi:plus"
+                    icon-position="left"
+                    button-class="w-auto px-4"
+                    label="Ajouter un groupe"
+                    @click="openCreate"
+                />
+            </div>
+        </div>
+
+        <DataTable
+            :columns="columns"
+            :items="items"
+            :loading="isLoading"
+            empty-message="Aucun groupe trouvé."
+            :deletable="!showArchived"
+            @row-click="openEdit"
+            @delete="(item) => handleDelete(item.id)"
+        >
+            <template #cell-color="{ item }">
+                <span
+                    class="inline-block h-6 w-6 rounded-full"
+                    :style="{ backgroundColor: item.color }"
+                />
+            </template>
+            <template #cell-description="{ item }">
+                {{ stripRichText(item.description) || '—' }}
+            </template>
+            <template #actions="{ item }">
+                <MalioButton
+                    v-if="!showArchived && canArchiveGroup(item)"
+                    variant="secondary"
+                    :label="$t('archive.archiveButton')"
+                    button-class="w-auto px-3"
+                    @click.stop="handleArchive(item)"
+                />
+                <MalioButton
+                    v-if="showArchived"
+                    variant="secondary"
+                    :label="$t('archive.unarchiveButton')"
+                    button-class="w-auto px-3"
+                    @click.stop="handleUnarchive(item)"
+                />
+            </template>
+        </DataTable>
+
+        <TaskGroupDrawer
+            v-model="drawerOpen"
+            :group="selectedItem"
+            :project-id="projectId"
+            :tasks="[...activeTasks, ...archivedTasks]"
+            @saved="onSaved"
+        />
+    </div>
+</template>
+
+<script setup lang="ts">
+import type { TaskGroup } from '~/modules/project-management/services/dto/task-group'
+import type { Task } from '~/modules/project-management/services/dto/task'
+import { useTaskGroupService } from '~/modules/project-management/services/task-groups'
+import { useTaskService } from '~/modules/project-management/services/tasks'
+import { stripRichText } from '~/utils/format'
+
+const props = defineProps<{
+    projectId: number
+}>()
+
+const emit = defineEmits<{
+    (e: 'updated'): void
+}>()
+
+import type { DataTableColumn } from '~/components/ui/DataTable.vue'
+
+const columns: DataTableColumn[] = [
+    { key: 'title', label: 'Titre', primary: true },
+    { key: 'color', label: 'Couleur' },
+    { key: 'description', label: 'Description', class: 'max-w-xs truncate text-neutral-700' },
+]
+
+const groupService = useTaskGroupService()
+const taskService = useTaskService()
+
+const allGroups = ref<TaskGroup[]>([])
+const activeTasks = ref<Task[]>([])
+const archivedTasks = ref<Task[]>([])
+const isLoading = ref(true)
+const drawerOpen = ref(false)
+const selectedItem = ref<TaskGroup | null>(null)
+const showArchived = ref(false)
+
+const items = computed(() =>
+    allGroups.value.filter(g => showArchived.value ? g.archived : !g.archived)
+)
+
+function canArchiveGroup(group: TaskGroup): boolean {
+    const groupTasks = activeTasks.value.filter(t => t.group?.id === group.id)
+    if (groupTasks.length === 0) return false
+    return groupTasks.every(t => t.status?.isFinal === true)
+}
+
+async function loadItems() {
+    isLoading.value = true
+    try {
+        const [g, t, at] = await Promise.all([
+            groupService.getByProject(props.projectId),
+            taskService.getByProject(props.projectId),
+            taskService.getByProject(props.projectId, true),
+        ])
+        allGroups.value = g
+        activeTasks.value = t
+        archivedTasks.value = at
+    } finally {
+        isLoading.value = false
+    }
+}
+
+function openCreate() {
+    selectedItem.value = null
+    drawerOpen.value = true
+}
+
+function openEdit(item: TaskGroup) {
+    selectedItem.value = item
+    drawerOpen.value = true
+}
+
+async function handleDelete(id: number) {
+    await groupService.remove(id)
+    await loadItems()
+    emit('updated')
+}
+
+async function handleArchive(group: TaskGroup) {
+    const groupTasks = activeTasks.value.filter(t => t.group?.id === group.id)
+    await Promise.all(groupTasks.map(t => taskService.update(t.id, { archived: true })))
+    await groupService.update(group.id, { archived: true })
+    await loadItems()
+    emit('updated')
+}
+
+async function handleUnarchive(group: TaskGroup) {
+    const groupTasks = archivedTasks.value.filter(t => t.group?.id === group.id)
+    await Promise.all(groupTasks.map(t => taskService.update(t.id, { archived: false })))
+    await groupService.update(group.id, { archived: false })
+    await loadItems()
+    emit('updated')
+}
+
+async function onSaved() {
+    await loadItems()
+    emit('updated')
+}
+
+onMounted(() => {
+    loadItems()
+})
+</script>