feat: 电商页面 KeepAlive 保活机制，切换页面不再丢失生成状态

通过 display:none 模式实现轻量 KeepAlive，电商页面首次访问后保持挂载，
切换到其他页面再切回时所有右侧面板状态（上传图片、生成进度、结果）完整保留。
同时清理项目中的临时文件和本地冗余图片。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/features/script-tokens/TokenUsagePage.tsx

@@ -142,6 +142,8 @@ function TokenUsagePage({
   onSelectView,
 }: TokenUsagePageProps) {
   const [enterpriseUsage, setEnterpriseUsage] = useState<WebEnterpriseUsageSummary | null>(null);
+  const [enterpriseUsageLoading, setEnterpriseUsageLoading] = useState(false);
+  const [enterpriseUsageError, setEnterpriseUsageError] = useState<string | null>(null);
   const isEnterpriseAdmin = session?.user.enterpriseRole === "admin";
   const isEnterpriseAccount = Boolean(session?.user.enterpriseId || session?.user.accountType === "enterprise");
 
@@ -152,10 +154,15 @@ function TokenUsagePage({
       setEnterpriseUsage(null);
       return;
     }
+    setEnterpriseUsageLoading(true);
+    setEnterpriseUsageError(null);
     try {
       setEnterpriseUsage(await loader());
     } catch (error) {
       setEnterpriseUsage(null);
+      setEnterpriseUsageError(error instanceof Error ? error.message : "加载失败");
+    } finally {
+      setEnterpriseUsageLoading(false);
     }
   }, [session, isEnterpriseAdmin, loadEnterpriseUsage, loadPersonalUsage]);