Add Today dashboard foundation with permission-aware KPI summary API.

Replace hardcoded Today cards with a backend summary endpoint and composable frontend widgets filtered by org type and tab permissions.

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

frontend/src/lib/api/today.ts

@@ -0,0 +1,14 @@
+import { apiClient } from './client';
+import type { TodaySummaryResponse } from '@/types/today';
+
+export interface TodaySummaryParams {
+  from: string;
+  to: string;
+}
+
+export const todayApi = {
+  summary: async (params: TodaySummaryParams): Promise<TodaySummaryResponse> => {
+    const response = await apiClient.get('/today/summary', { params });
+    return response.data;
+  },
+};