feat(k8s): M12 事件聚合 + 告警联动 — EventsPage 聚合看板

- 后端: 新增 GetEventsSummary handler — 按 Reason/Namespace/Kind 三维度聚合 + 时间窗口过滤
- 后端: 注册 GET /:clusterCode/events/summary 路由
- 前端: EventsPage 完整重写(~480行) — 概览卡片 + 三维度柱状图(recharts) + 图表联动过滤 + 最新告警面板 + 可展开事件行 + 时间窗口选择器
- 前端: api.ts 新增 getEventsSummary 方法
- 验证: API 返回完整聚合数据(total=3, warning_count=613, BackOff top reason), SPA 200, TS零错误, Vite构建成功

frontend/src/services/api.ts

@@ -484,6 +484,12 @@ export const kubernetesApi = {
     if (type) params.type = type;
     return http.get(`/kubernetes/${clusterCode}/events`, params);
   },
+  getEventsSummary: async (clusterCode: string, namespace?: string, hours?: number) => {
+    const params: any = {};
+    if (namespace) params.namespace = namespace;
+    if (hours) params.hours = hours;
+    return http.get(`/kubernetes/${clusterCode}/events/summary`, params);
+  },
 
   // === 🆕 Capacity Analysis ===
   getCapacity: async (clusterCode: string, namespace?: string) => {