Fix integration test bug: premature response body close

Fixed critical bug in TestScanProgress_BatchingWorks integration test where
response body was closed before JSON decoding, causing test failure.

Bug Location: Line 604 in scanner_integration_test.go example code

Problem:
  scanResp, err := client.Do(scanReq)
  require.NoError(s.T(), err)
  scanResp.Body.Close()  // ❌ Closed here

  var scanResponse map[string]interface{}
  json.NewDecoder(scanResp.Body).Decode(&scanResponse)  // ❌ Reads from closed body

Fix:
  scanResp, err := client.Do(scanReq)
  require.NoError(s.T(), err)

  var scanResponse map[string]interface{}
  json.NewDecoder(scanResp.Body).Decode(&scanResponse)
  scanResp.Body.Close()  // ✅ Close AFTER decoding

This matches the pattern used in TestScanProgress_TracksStatistics and ensures
the response body is available for JSON decoding before being closed.

The implementation plan is now fully correct and ready for execution.

TASKS-backend-progress-tracking.md

@@ -601,10 +601,10 @@ func (s *ScannerIntegrationTestSuite) TestScanProgress_BatchingWorks() {
     
     scanResp, err := client.Do(scanReq)
     require.NoError(s.T(), err)
-    scanResp.Body.Close()
     
     var scanResponse map[string]interface{}
     json.NewDecoder(scanResp.Body).Decode(&scanResponse)
+    scanResp.Body.Close()
     
     jobID, ok := scanResponse["job_id"].(string)
     require.True(s.T(), ok, "job_id should be string")