feat(usage): add cost trend chart with hourly/daily toggle

src/pages/UsagePage.tsx

@@ -26,6 +26,7 @@ import {
   PriceSettingsCard,
   CredentialStatsCard,
   TokenBreakdownChart,
+  CostTrendChart,
   useUsageData,
   useSparklines,
   useChartData
@@ -367,6 +368,16 @@ export function UsagePage() {
         hourWindowHours={hourWindowHours}
       />
 
+      {/* Cost Trend Chart */}
+      <CostTrendChart
+        usage={filteredUsage}
+        loading={loading}
+        isDark={isDark}
+        isMobile={isMobile}
+        modelPrices={modelPrices}
+        hourWindowHours={hourWindowHours}
+      />
+
       {/* Details Grid */}
       <div className={styles.detailsGrid}>
         <ApiDetailsCard apiStats={apiStats} loading={loading} hasPrices={hasPrices} />