fix(security): prevent integer overflow in uint64 to int64 conversions

Add overflow checks before converting uint64 memory values to int64
to prevent potential integer overflow issues identified by gosec (G115).

- Add math.MaxInt64 checks in fileproc/backpressure.go
- Add math.MaxInt64 checks in fileproc/resource_monitor_validation.go
- Add math.MaxInt64 checks in fileproc/resource_monitor_metrics.go
- Add math.MaxInt64 check in benchmark/benchmark.go with nosec annotation

Co-authored-by: ivuorinen <11024+ivuorinen@users.noreply.github.com>

fileproc/resource_monitor_metrics_test.go

@@ -46,4 +46,4 @@ func TestResourceMonitor_Metrics(t *testing.T) {
 	if !metrics.LastUpdated.After(time.Now().Add(-time.Second)) {
 		t.Error("Expected recent LastUpdated timestamp")
 	}
-}
+}