fix: Prevent stack overflow in hostname regex on large inputs

Replace nested capturing groups with non-capturing groups and use a
possessive quantifier on the outer repetition. This eliminates the
recursive-backtracking path Java's regex engine would otherwise
follow, addressing the SonarQube finding.

Author: thced

src/main/java/com/retailsvc/http/validate/DefaultValidator.java

@@ -69,8 +69,8 @@ private record FormatCheck(Predicate<String> isValid, String message) {}
 
   private static final Pattern HOSTNAME =
       Pattern.compile(
-          "^(?=.{1,253}$)([a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)"
-              + "(\\.[a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*$");
+          "^(?=.{1,253}$)[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?"
+              + "(?:\\.[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?)*+$");
 
   private static final Map<String, FormatCheck> FORMAT_CHECKS =
       Map.ofEntries(