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/services/dto/notification.ts

@@ -1,4 +1,4 @@
-export type NotificationType = 'ticket_created' | 'ticket_status_changed'
+export type NotificationType = 'task_assigned' | 'task_collaborator_added'
 
 export type Notification = {
     '@id'?: string
@@ -7,7 +7,6 @@ export type Notification = {
     type: NotificationType
     title: string
     message: string
-    relatedTicket: string | null
     isRead: boolean
     createdAt: string
 }