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/PricingEditModal.tsx

@@ -106,7 +106,9 @@ export function PricingEditModal({
                 onChange={(e) =>
                   setFormData({ ...formData, modelId: e.target.value })
                 }
-                placeholder="例如: claude-3-5-sonnet-20241022"
+                placeholder={t("usage.modelIdPlaceholder", {
+                  defaultValue: "例如: claude-3-5-sonnet-20241022",
+                })}
                 required
               />
             </div>
@@ -122,7 +124,9 @@ export function PricingEditModal({
               onChange={(e) =>
                 setFormData({ ...formData, displayName: e.target.value })
               }
-              placeholder="例如: Claude 3.5 Sonnet"
+              placeholder={t("usage.displayNamePlaceholder", {
+                defaultValue: "例如: Claude 3.5 Sonnet",
+              })}
               required
             />
           </div>