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/services/dto/task.ts

@@ -0,0 +1,62 @@
+import type { TaskStatus } from './task-status'
+import type { TaskEffort } from './task-effort'
+import type { TaskPriority } from './task-priority'
+import type { TaskTag } from './task-tag'
+import type { TaskGroup } from './task-group'
+import type { UserData } from '~/services/dto/user-data'
+import type { Project } from './project'
+import type { TaskDocument } from './task-document'
+
+export type Task = {
+    id: number
+    '@id'?: string
+    number: number
+    title: string
+    description: string | null
+    status: TaskStatus | null
+    effort: TaskEffort | null
+    priority: TaskPriority | null
+    assignee: UserData | null
+    collaborators: UserData[]
+    group: TaskGroup | null
+    project: Project | null
+    tags: TaskTag[]
+    documents: TaskDocument[]
+    archived: boolean
+    scheduledStart: string | null
+    scheduledEnd: string | null
+    deadline: string | null
+    syncToCalendar: boolean
+    calendarSyncError: string | null
+    recurrence: {
+        id: number
+        '@id'?: string
+        type: 'daily' | 'weekly' | 'monthly' | 'yearly'
+        interval: number
+        daysOfWeek: string[] | null
+        dayOfMonth: number | null
+        weekOfMonth: number | null
+        endDate: string | null
+        maxOccurrences: number | null
+        occurrenceCount: number
+    } | null
+}
+
+export type TaskWrite = {
+    title: string
+    description: string | null
+    status: string | null
+    effort: string | null
+    priority: string | null
+    assignee: string | null
+    collaborators?: string[]
+    group: string | null
+    project: string
+    tags: string[]
+    archived?: boolean
+    scheduledStart?: string | null
+    scheduledEnd?: string | null
+    deadline?: string | null
+    syncToCalendar?: boolean
+    recurrence?: string | null
+}