fix(dashboard): Set secret flag when mapping struct fields to field configs

The struct-field-to-custom-field-config mapping did not set `secret`, which became
a required property once the custom-field config type started selecting it. Struct
sub-fields cannot be secret, so it is set to false.

Relates to #2648

Author: michaelbromley

packages/dashboard/src/lib/framework/form-engine/form-schema-tools.ts

@@ -37,6 +37,7 @@ function mapGraphQLCustomFieldToConfig(field: StructField) {
         readonly: false,
         requiresPermission: [],
         nullable: true, // Default to true since GraphQL fields are nullable by default
+        secret: false, // struct sub-fields cannot be secret
     };
 
     switch (field.__typename) {