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/pages/admin.vue

@@ -27,7 +27,6 @@
             <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'" />
@@ -57,7 +56,6 @@ 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' },