fix: health check treats 4xx as success (WAF reachable, just no index page)

health.go

@@ -24,11 +24,13 @@ func startHealthCheck() {
 			breaker.RecordFailure()
 		} else {
 			resp.Body.Close()
-				if resp.StatusCode < 500 {
-					breaker.RecordSuccess()
-				} else {
+			// Any response (2xx, 3xx, 4xx) means WAF is reachable.
+			// Only 5xx or connection errors indicate the WAF is unhealthy.
+			if resp.StatusCode >= 500 {
 				log.Printf("WAF health check: status %d", resp.StatusCode)
 				breaker.RecordFailure()
+			} else {
+				breaker.RecordSuccess()
 			}
 		}