refactor: improve type safety and remove forced casts in dashboard service

shared/modules/dashboard/dashboard.service.ts

@@ -141,7 +141,9 @@ export const dashboardService = {
             const { systemEvents, EVENTS } = await import("@shared/lib/events");
             systemEvents.emit(EVENTS.DASHBOARD.NEW_EVENT, {
                 ...fullEvent,
-                timestamp: (fullEvent.timestamp as Date).toISOString()
+                timestamp: (fullEvent.timestamp instanceof Date)
+                    ? fullEvent.timestamp.toISOString()
+                    : fullEvent.timestamp
             });
         } catch (e) {
             console.error("Failed to emit system event:", e);