feat: dashboard top hosts/types, problems 24h, drill-down (d2-2)

- Extend /dashboards/summary; Events filters from query (hostname, severity)

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

frontend/src/api.ts

@@ -137,6 +137,17 @@ export async function resolveProblem(problemId: number): Promise<{ id: number; s
   return apiFetch(`/api/v1/problems/${problemId}/resolve`, { method: "POST" });
 }
 
+export interface TopHostItem {
+  host_id: number;
+  hostname: string;
+  count: number;
+}
+
+export interface TopTypeItem {
+  type: string;
+  count: number;
+}
+
 export interface DashboardSummary {
   events_last_24h: number;
   hosts_total: number;
@@ -144,6 +155,10 @@ export interface DashboardSummary {
   heartbeats_24h: number;
   daily_reports_24h: number;
   problems_open: number;
+  problems_opened_24h: number;
+  problems_resolved_24h: number;
   severity_24h: Record<string, number>;
+  top_hosts: TopHostItem[];
+  top_event_types: TopTypeItem[];
   recent_events: EventSummary[];
 }