refactor: extract error message handling to utils module

- Move extractErrorMessage function from App.tsx to utils/errorUtils.ts
- Improve code organization and reusability
- Enhance error notification with dynamic message extraction and timeout

src/utils/errorUtils.ts

@@ -0,0 +1,38 @@
+/**
+ * 从各种错误对象中提取错误信息
+ * @param error 错误对象
+ * @returns 提取的错误信息字符串
+ */
+export const extractErrorMessage = (error: unknown): string => {
+  if (!error) return "";
+  if (typeof error === "string") {
+    return error;
+  }
+  if (error instanceof Error && error.message.trim()) {
+    return error.message;
+  }
+
+  if (typeof error === "object") {
+    const errObject = error as Record<string, unknown>;
+
+    const candidate = errObject.message ?? errObject.error ?? errObject.detail;
+    if (typeof candidate === "string" && candidate.trim()) {
+      return candidate;
+    }
+
+    const payload = errObject.payload;
+    if (typeof payload === "string" && payload.trim()) {
+      return payload;
+    }
+    if (payload && typeof payload === "object") {
+      const payloadObj = payload as Record<string, unknown>;
+      const payloadCandidate =
+        payloadObj.message ?? payloadObj.error ?? payloadObj.detail;
+      if (typeof payloadCandidate === "string" && payloadCandidate.trim()) {
+        return payloadCandidate;
+      }
+    }
+  }
+
+  return "";
+};