feat(client-portal) : portal front + client account admin (phases 1-2 front)

LST-69 (3.2) front. Client portal UI on the phase-1 backend.

- New frontend/modules/client-portal/ layer: /portal (project cards from the
  client's allowedProjects via /me), /portal/projects/[id] (tickets list,
  detail modal, create modal with document upload), client-tickets service +
  DTO, CT-XXX formatting.
- Front tenancy: auth.global.ts redirects a pure ROLE_CLIENT to /portal and
  blocks internal routes; portal pages open to any authenticated user.
- Admin: UserDrawer manages client accounts (ROLE_CLIENT + client +
  allowedProjects); new "Tickets client" admin tab (list, filters, status
  change with required comment on reject, detail modal).
- Kanban/my-tasks: client-ticket icon + tooltip when task.clientTicket is set
  (data via task:read, no extra call). TaskDocument upload generalized with a
  clientTicketId prop. getContent uses native fetch (text response).
- i18n portal/clientTicket keys; sidebar /portal item (module client-portal).

nuxt build passes; /portal routes present, existing routes intact.

frontend/pages/admin.vue

@@ -27,6 +27,7 @@
             <AdminPriorityTab v-if="activeTab === 'priorities'" />
             <AdminTagTab v-if="activeTab === 'tags'" />
             <AdminUserTab v-if="activeTab === 'users'" />
+            <AdminClientTicketTab v-if="activeTab === 'clientTickets'" />
             <AdminRoleTab v-if="activeTab === 'roles' && canViewRoles" />
             <AdminAuditTab v-if="activeTab === 'audit' && canViewAudit" />
             <AdminGiteaTab v-if="activeTab === 'gitea'" />
@@ -56,6 +57,7 @@ const tabs = [
     { key: 'priorities', label: 'Priorités' },
     { key: 'tags', label: 'Tags' },
     { key: 'users', label: 'Utilisateurs' },
+    { key: 'clientTickets', label: t('clientTicket.adminTab') },
     { key: 'roles', label: t('admin.roles.title'), permission: 'core.roles.view' },
     { key: 'audit', label: t('admin.audit.title'), permission: 'core.audit_log.view' },
     { key: 'gitea', label: 'Gitea' },