refactor(client-portal) : remove client portal feature entirely

- drop ClientPortal module, ClientTicket entity, ROLE_CLIENT and all couplings (Task, TaskDocument, User, Notification) back to an internal-only model

- migration drops client_ticket / user_allowed_projects / related FK columns and removes leftover external client accounts (would otherwise be promoted to ROLE_USER)

- remove client-portal frontend module, admin tickets tab, user portal section, portal nav item and portal/clientTicket i18n keys

- fix directory nav icon (invalid mdi:contact-multiple-outline -> mdi:card-account-details-outline)

- add 'make sync-permissions' target, wire it into install/db-reset and the prod deploy script

frontend/modules/project-management/services/dto/task.ts

@@ -28,14 +28,6 @@ export type Task = {
     deadline: string | null
     syncToCalendar: boolean
     calendarSyncError: string | null
-    clientTicket: {
-        id: number
-        '@id'?: string
-        number: number
-        type: 'bug' | 'improvement' | 'other'
-        status: 'new' | 'in_progress' | 'done' | 'rejected'
-        title: string
-    } | null
     recurrence: {
         id: number
         '@id'?: string