Fix candidate mileage review findings

go/vehicle-gateway/internal/stats/source_mileage_test.go

@@ -50,8 +50,9 @@ func TestUpsertSourceMileageWritesCandidateRow(t *testing.T) {
 	for _, want := range []string{
 		"INSERT INTO vehicle_daily_mileage_source",
 		"ON DUPLICATE KEY UPDATE",
-		"daily_mileage_km = VALUES(daily_mileage_km)",
+		"daily_mileage_km = GREATEST(",
 		"quality_status = VALUES(quality_status)",
+		"platform_name = COALESCE(NULLIF(TRIM(VALUES(platform_name)), ''), platform_name)",
 	} {
 		if !strings.Contains(sql, want) {
 			t.Fatalf("candidate upsert missing %q: %s", want, sql)
@@ -61,3 +62,22 @@ func TestUpsertSourceMileageWritesCandidateRow(t *testing.T) {
 		t.Fatalf("first arg = %#v", got)
 	}
 }
+
+func TestUpsertSourceMileageSkipsBlankSourceIP(t *testing.T) {
+	exec := &recordingExec{}
+	sample := SourceMileageSample{
+		VIN:           "LA9GG64L7PBAF4001",
+		StatDate:      "2026-07-08",
+		Protocol:      envelope.ProtocolJT808,
+		SourceKey:     "JT808:13307765812@",
+		SourceIP:      "   ",
+		Phone:         "13307765812",
+		QualityStatus: QualityOK,
+	}
+	if err := UpsertSourceMileage(context.Background(), exec, sample); err != nil {
+		t.Fatalf("UpsertSourceMileage() error = %v", err)
+	}
+	if len(exec.calls) != 0 {
+		t.Fatalf("exec calls = %d, want 0", len(exec.calls))
+	}
+}