fix(web): improve network error message with i18n

- Replace hardcoded 'Network error' with i18n key 'apiError.networkError'
- Add dedicated handler for status 0 in handleApiError
- Add test case for network error scenario

Closes #160

web/src/api/client.ts

@@ -213,7 +213,7 @@ export async function fetchJson<T>(input: RequestInfo | URL, init?: RequestWithT
     if (error instanceof DOMException && error.name === 'AbortError') {
       throw new ApiError('error.request.timeout', 408)
     }
-    throw new ApiError('Network error', 0)
+    throw new ApiError('apiError.networkError', 0)
   } finally {
     cleanup()
   }

web/src/shared/lib/api-error.test.ts

@@ -53,4 +53,14 @@ describe('handleApiError', () => {
 
     expect(errorSpy).toHaveBeenLastCalledWith('Server said no')
   })
+
+  it('shows network error message for status 0', async () => {
+    const { ApiError, handleApiError } = await import('./api-error')
+
+    handleApiError(new ApiError('apiError.networkError', 0))
+
+    expect(errorSpy).toHaveBeenCalled()
+    const lastCall = errorSpy.mock.calls[errorSpy.mock.calls.length - 1][0]
+    expect(lastCall).toMatch(/network|网络/)
+  })
 })

web/src/shared/lib/api-error.ts

@@ -52,6 +52,11 @@ export function handleApiError(error: unknown): void {
 
   const { status } = error
 
+  if (status === 0) {
+    toast.error(i18n.t('apiError.networkError'))
+    return
+  }
+
   if (status === 401) {
     if (isAccountDisabledError(error)) {
       window.location.href = `/login?reason=${ACCOUNT_DISABLED_REASON}`