feat(usage): enhance dashboard with auto-refresh control and robust formatting (#942)

* style: format code and apply clippy lint fixes

* feat(usage): enhance dashboard with auto-refresh control and robust formatting

- Add configurable auto-refresh interval toggle (off/5s/10s/30s/60s) to usage dashboard
- Extract shared format utilities (fmtUsd, fmtInt, parseFiniteNumber, getLocaleFromLanguage)
- Refactor request log time filtering to rolling vs fixed mode with validation
- Use stable serializable query keys instead of filter objects
- Handle NaN/Infinity safely in number formatting across all usage components
- Use RFC 3339 date format in backend trend data

src/components/usage/UsageSummaryCards.tsx

@@ -4,19 +4,26 @@ import { Card, CardContent } from "@/components/ui/card";
 import { useUsageSummary } from "@/lib/query/usage";
 import { Activity, DollarSign, Layers, Database, Loader2 } from "lucide-react";
 import { motion } from "framer-motion";
+import { fmtUsd, parseFiniteNumber } from "./format";
 
 interface UsageSummaryCardsProps {
   days: number;
+  refreshIntervalMs: number;
 }
 
-export function UsageSummaryCards({ days }: UsageSummaryCardsProps) {
+export function UsageSummaryCards({
+  days,
+  refreshIntervalMs,
+}: UsageSummaryCardsProps) {
   const { t } = useTranslation();
 
-  const { data: summary, isLoading } = useUsageSummary(days);
+  const { data: summary, isLoading } = useUsageSummary(days, {
+    refetchInterval: refreshIntervalMs > 0 ? refreshIntervalMs : false,
+  });
 
   const stats = useMemo(() => {
     const totalRequests = summary?.totalRequests ?? 0;
-    const totalCost = parseFloat(summary?.totalCost || "0");
+    const totalCost = parseFiniteNumber(summary?.totalCost);
 
     const inputTokens = summary?.totalInputTokens ?? 0;
     const outputTokens = summary?.totalOutputTokens ?? 0;
@@ -37,7 +44,7 @@ export function UsageSummaryCards({ days }: UsageSummaryCardsProps) {
       },
       {
         title: t("usage.totalCost"),
-        value: `$${totalCost.toFixed(4)}`,
+        value: totalCost == null ? "--" : fmtUsd(totalCost, 4),
         icon: DollarSign,
         color: "text-green-500",
         bg: "bg-green-500/10",