fix: improve trader error feedback, stale balance cleanup, and claw402 warnings (#1452)

* fix: improve trader error handling and balance validation

* fix: localize structured trader failure reasons

---------

Co-authored-by: apple <apple@MacbookPro-zbh.local>

web/src/lib/httpClient.ts

@@ -19,6 +19,28 @@ export interface ApiResponse<T = any> {
   success: boolean
   data?: T
   message?: string
+  errorKey?: string
+  errorParams?: Record<string, string>
+  statusCode?: number
+}
+
+export class ApiError extends Error {
+  errorKey?: string
+  errorParams?: Record<string, string>
+  statusCode?: number
+
+  constructor(
+    message: string,
+    errorKey?: string,
+    errorParams?: Record<string, string>,
+    statusCode?: number
+  ) {
+    super(message)
+    this.name = 'ApiError'
+    this.errorKey = errorKey
+    this.errorParams = errorParams
+    this.statusCode = statusCode
+  }
 }
 
 /**
@@ -86,6 +108,13 @@ export class HttpClient {
    */
   private async handleError(error: AxiosError): Promise<any> {
     const isSilent = (error.config as any)?.silentError === true
+    const errorData = error.response?.data as {
+      error?: string
+      message?: string
+      error_key?: string
+      error_params?: Record<string, string>
+    } | undefined
+    const serverMessage = errorData?.error || errorData?.message
 
     // Network error (no response from server)
     if (!error.response) {
@@ -98,10 +127,7 @@ export class HttpClient {
       throw new Error('Network error')
     }
 
-    const { status } = error.response as AxiosResponse<{
-      error?: string
-      message?: string
-    }>
+    const status = error.response?.status ?? 0
 
     // Handle 401 Unauthorized
     if (status === 401) {
@@ -159,6 +185,9 @@ export class HttpClient {
 
     // Handle 500+ Server Error - system error
     if (status >= 500) {
+      if (serverMessage) {
+        return Promise.reject(error)
+      }
       if (!isSilent) {
         toast.error('Server Error', {
           id: 'server-error',
@@ -212,6 +241,9 @@ export class HttpClient {
         return {
           success: false,
           message: errorData?.error || errorData?.message || 'Operation failed',
+          errorKey: errorData?.error_key,
+          errorParams: errorData?.error_params,
+          statusCode: error.response.status,
         }
       }