feat: UI Problems list filters, detail card and event timeline (d2-1)

- Filters status/severity/hostname; /problems/:id with Ack/Resolve and timeline

- Dashboard drill-down to open problems

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/router.ts

@@ -5,6 +5,7 @@ import EventDetailView from "./views/EventDetailView.vue";
 import HostsView from "./views/HostsView.vue";
 import LoginView from "./views/LoginView.vue";
 import ProblemsView from "./views/ProblemsView.vue";
+import ProblemDetailView from "./views/ProblemDetailView.vue";
 import DashboardView from "./views/DashboardView.vue";
 import ReportsView from "./views/ReportsView.vue";
 
@@ -19,6 +20,7 @@ const router = createRouter({
     { path: "/reports", component: ReportsView },
     { path: "/hosts", component: HostsView },
     { path: "/problems", component: ProblemsView },
+    { path: "/problems/:id", component: ProblemDetailView, props: true },
   ],
 });