refactor(handlers): extract request validation logic to new function

Extract the request validation logic from ValidateRequest into a new ValidateRequestWithBody function to allow passing pre-read request bodies. Update all handler functions to use the new validation function for consistency and to avoid duplicate body reading.

handlers.go

@@ -202,6 +202,10 @@ func ValidateRequest(w http.ResponseWriter, r *http.Request, requiredFields ...s
 	}
 	defer r.Body.Close()
 
+	return ValidateRequestWithBody(w, r, body, requiredFields...)
+}
+
+func ValidateRequestWithBody(w http.ResponseWriter, r *http.Request, body []byte, requiredFields ...string) (int, string, error) {
 	var reqMap map[string]interface{}
 	if err := json.Unmarshal(body, &reqMap); err != nil {
 		return 0, "", errors.New("invalid request format")