Refactor: Improve type safety for UsageMetricsChart data

Co-authored-by: db2002dominic <db2002dominic@gmail.com>

ui/app/usage/page.tsx

@@ -137,7 +137,7 @@ export default function UsagePage() {
               ) : metricsData && metricsData.metrics.length > 0 ? (
                 <>
                   <UsageMetricsChart
-                    data={metricsData.metrics}
+                    data={metricsData.metrics as Array<Record<string, unknown> & { timestamp: string }>}
                     title='Request Volume'
                     dataKeys={[
                       {
@@ -164,7 +164,7 @@ export default function UsagePage() {
                       refunds_sats: m.refunds_msats / 1000,
                       net_revenue_sats:
                         (m.revenue_msats - m.refunds_msats) / 1000,
-                    }))}
+                    })) as Array<Record<string, unknown> & { timestamp: string }>}
                     title='Revenue Over Time (sats)'
                     dataKeys={[
                       {
@@ -185,7 +185,7 @@ export default function UsagePage() {
                     ]}
                   />
                   <UsageMetricsChart
-                    data={metricsData.metrics}
+                    data={metricsData.metrics as Array<Record<string, unknown> & { timestamp: string }>}
                     title='Error Tracking'
                     dataKeys={[
                       {
@@ -206,7 +206,7 @@ export default function UsagePage() {
                     ]}
                   />
                   <UsageMetricsChart
-                    data={metricsData.metrics}
+                    data={metricsData.metrics as Array<Record<string, unknown> & { timestamp: string }>}
                     title='Payment Activity'
                     dataKeys={[
                       {

ui/components/usage-metrics-chart.tsx

@@ -11,13 +11,12 @@ import {
   Legend,
   CartesianGrid,
 } from 'recharts';
-import { UsageMetricData } from '@/lib/api/services/admin';
 
 interface UsageMetricsChartProps {
-  data: UsageMetricData[];
+  data: Array<Record<string, unknown> & { timestamp: string }>;
   title: string;
   dataKeys: Array<{
-    key: keyof UsageMetricData;
+    key: string;
     name: string;
     color: string;
   }>;

ui/lib/api/services/admin.ts

@@ -859,6 +859,7 @@ export interface UsageMetricData {
   upstream_errors: number;
   revenue_msats: number;
   refunds_msats: number;
+  [key: string]: unknown;
 }
 
 export interface UsageMetrics {