feat: host heartbeat status and dashboard metrics (2.2)

Track agent.heartbeat and report.daily.ssh per host; show online/stale
on Hosts UI; dashboard counters and SAC_HEARTBEAT_STALE_MINUTES config.

frontend/src/views/EventsView.vue

@@ -57,8 +57,11 @@
 
 <script setup lang="ts">
 import { onMounted, ref } from "vue";
+import { useRoute } from "vue-router";
 import { apiFetch, type EventListResponse } from "../api";
 
+const route = useRoute();
+
 const data = ref<EventListResponse | null>(null);
 const loading = ref(false);
 const error = ref("");
@@ -92,5 +95,9 @@ async function load(p: number) {
   }
 }
 
-onMounted(() => load(1));
+onMounted(() => {
+  const t = route.query.type;
+  if (typeof t === "string" && t) typeFilter.value = t;
+  load(1);
+});
 </script>