feat(client-portal) : phase 3 — ticket notifications

LST-69 (3.2) phase 3. Wires the existing notification system to client-ticket
events (the bell/useNotifications/endpoints already existed).

- Notification.relatedTicket (ManyToOne ClientTicketInterface, SET NULL) +
  additive migration + notification:read group.
- NotifierInterface::notify() gains a backward-compatible optional
  relatedTicket param (existing callers unchanged).
- ClientTicketNumberProcessor (POST): notifies all ROLE_ADMIN users
  (ticket_created), tolerant try/catch after flush. ClientTicketStatusProcessor
  (PATCH): notifies submittedBy on status change (ticket_status_changed).
- Front: notification DTO relatedTicket; NotificationBell navigates to /admin
  (admin) or /portal (client) on ticket notifications.

180 tests green (178 + 2), nuxt build passes, cs-fixer clean.

frontend/components/notification/NotificationBell.vue

@@ -102,11 +102,22 @@ function toggleDropdown() {
     }
 }
 
+const auth = useAuthStore()
+
+const isAdmin = computed(() => (auth.user?.roles ?? []).includes('ROLE_ADMIN'))
+
 function handleClick(notif: Notification) {
     if (!notif.isRead) {
         markAsRead(notif.id)
     }
     isOpen.value = false
+
+    // Deep-link to the related ticket when present. The notification payload does
+    // not carry the ticket's project, so we route to the relevant list view:
+    // admins to the client-tickets admin tab, clients to their portal.
+    if (notif.relatedTicket) {
+        navigateTo(isAdmin.value ? '/admin' : '/portal')
+    }
 }
 
 async function handleMarkAllRead() {