i18n: complete internationalization for provider and usage query panels

- Add 45+ new translation keys for usage query and usage script features
- Fix duplicate provider object in translation files that caused missing translations
- Remove all hardcoded Chinese text and defaultValue fallbacks from components
- Add proper translations for:
  * Usage footer (query status, plan usage display)
  * Usage script modal (script editor, validation, test controls)
  * Provider forms (basic fields, endpoints, model selectors)
  * Provider dialogs (add/edit hints and titles)

Modified 16 files:
- 2 translation files (zh.json, en.json)
- 14 component files (removed defaultValue, added t() calls)

All UI text now properly supports Chinese/English switching.

src/components/providers/ProviderEmptyState.tsx

@@ -15,16 +15,14 @@ export function ProviderEmptyState({ onCreate }: ProviderEmptyStateProps) {
         <Users className="h-7 w-7 text-muted-foreground" />
       </div>
       <h3 className="text-lg font-semibold">
-        {t("provider.noProviders", { defaultValue: "暂无供应商" })}
+        {t("provider.noProviders")}
       </h3>
       <p className="mt-2 max-w-sm text-sm text-muted-foreground">
-        {t("provider.noProvidersDescription", {
-          defaultValue: "开始添加一个供应商以快速完成切换。",
-        })}
+        {t("provider.noProvidersDescription")}
       </p>
       {onCreate && (
         <Button className="mt-6" onClick={onCreate}>
-          {t("provider.addProvider", { defaultValue: "添加供应商" })}
+          {t("provider.addProvider")}
         </Button>
       )}
     </div>