i18n: complete internationalization for v3.8+ features

- Add health status translations (operational, degraded, failed, circuitOpen)
- Add proxy panel translations (serviceAddress, stats, stopped state)
- Add usage filter translations (appType, statusCode, searchPlaceholder)
- Add providerIcon click hints (clickToChange, clickToSelect)
- Add config load error translations for main.tsx
- Complete Japanese proxy section (failoverQueue, autoFailover)
- Fix date/time locale in usage charts and tables
- Use t() function in all hardcoded UI strings

src/components/usage/UsageTrendChart.tsx

@@ -17,7 +17,7 @@ interface UsageTrendChartProps {
 }
 
 export function UsageTrendChart({ days }: UsageTrendChartProps) {
-  const { t } = useTranslation();
+  const { t, i18n } = useTranslation();
   const { data: trends, isLoading } = useUsageTrends(days);
 
   if (isLoading) {
@@ -29,14 +29,20 @@ export function UsageTrendChart({ days }: UsageTrendChartProps) {
   }
 
   const isToday = days === 1;
+  const dateLocale =
+    i18n.language === "zh"
+      ? "zh-CN"
+      : i18n.language === "ja"
+        ? "ja-JP"
+        : "en-US";
   const chartData =
     trends?.map((stat) => {
       const pointDate = new Date(stat.date);
       return {
         rawDate: stat.date,
         label: isToday
-          ? pointDate.toLocaleTimeString("zh-CN", { hour: "2-digit" })
-          : pointDate.toLocaleDateString("zh-CN", {
+          ? pointDate.toLocaleTimeString(dateLocale, { hour: "2-digit" })
+          : pointDate.toLocaleDateString(dateLocale, {
               month: "2-digit",
               day: "2-digit",
             }),