refactor: 🎨 update dashboard activity data structure to use timestamps and add local hour bucketing

frontend/src/api.ts

@@ -213,7 +213,7 @@ export const api = {
         available: number;
         status: "active" | "alerting";
       }[];
-      activity: { hour: number; count: number }[];
+      activity: string[];
     }>(await fetchApi("/api/v2/dashboard"));
   },
   async search(q: string) {

frontend/src/utils/datetime.ts

@@ -21,3 +21,14 @@ export function formatLocalTime(ts?: string | null, fallback = "—"): string {
   if (!d) return ts?.trim() || fallback;
   return d.toLocaleString();
 }
+
+/** Bucket audit timestamps from the last 24h by local hour of day (0–23). */
+export function bucketActivityByLocalHour(timestamps: string[]): { hour: number; count: number }[] {
+  const counts = new Array<number>(24).fill(0);
+  for (const ts of timestamps) {
+    const d = parseApiTimestamp(ts);
+    if (!d) continue;
+    counts[d.getHours()]++;
+  }
+  return counts.map((count, hour) => ({ hour, count }));
+}

frontend/src/views/DashboardView.vue

@@ -3,6 +3,7 @@ import { ref, onMounted, computed } from "vue";
 import { RouterLink } from "vue-router";
 import { Network, Wifi, Layers, Server } from "lucide-vue-next";
 import { api } from "@/api";
+import { bucketActivityByLocalHour } from "@/utils/datetime";
 
 interface DashboardStats {
   total_ips: number;
@@ -46,7 +47,7 @@ onMounted(async () => {
     const d = await api.dashboard();
     stats.value = d.stats;
     subnetOverview.value = d.subnet_overview;
-    activity.value = d.activity;
+    activity.value = bucketActivityByLocalHour(d.activity);
   } catch (e) {
     error.value = e instanceof Error ? e.message : "Failed to load dashboard";
   } finally {