perf: load dashboard metrics from analytics API

src/dataService.ts

@@ -1,4 +1,4 @@
-import type { CampaignPreview, CampaignProcessSummary, CampaignQueueSummary, OrderData, StockData } from './types';
+import type { CampaignPreview, CampaignProcessSummary, CampaignQueueSummary, DashboardAnalytics, DateRange, OrderData, StockData } from './types';
 
 const API_URL = import.meta.env.VITE_API_URL || '/api';
 
@@ -89,6 +89,28 @@ const authFetch = async (path: string, options: RequestInit = {}): Promise<Respo
     return response;
 };
 
+const formatDateParam = (date: Date): string => {
+    const year = date.getFullYear();
+    const month = String(date.getMonth() + 1).padStart(2, '0');
+    const day = String(date.getDate()).padStart(2, '0');
+    return `${year}-${month}-${day}`;
+};
+
+export const fetchDashboardAnalytics = async (dateRange: DateRange): Promise<DashboardAnalytics | null> => {
+    try {
+        const params = new URLSearchParams({
+            start: formatDateParam(dateRange.start),
+            end: formatDateParam(dateRange.end)
+        });
+        const response = await authFetch(`/analytics/dashboard?${params.toString()}`);
+        if (!response.ok) return null;
+        return await response.json();
+    } catch (error) {
+        console.error('Fetch dashboard analytics failed', error);
+        return null;
+    }
+};
+
 export const fetchCampaigns = async (): Promise<CampaignQueueSummary | null> => {
     try {
         const response = await authFetch('/campaigns');