Skip write_lobs callback when using prepared statements

When prepared_statements is enabled (the default), LOB data is already
written during INSERT via temporary LOB binding in type_cast(). The
write_lobs callback was redundantly writing the same data again via
SELECT FOR UPDATE.

This change skips the callback in the prepared statements path while
preserving it for the unprepared path, where empty_clob()/empty_blob()
literals require the callback to populate LOB data after INSERT.

Fixes the double-write issue identified in #2483.

Author: andynu

lib/active_record/connection_adapters/oracle_enhanced/lob.rb

@@ -27,6 +27,9 @@ def lob_columns
 
         private
           def enhanced_write_lobs
+            # Skip if using prepared statements - LOB data is already written via temp LOB binding
+            return if self.class.connection.prepared_statements
+
             if self.class.connection.is_a?(ConnectionAdapters::OracleEnhancedAdapter) &&
                 !(self.class.custom_create_method || self.class.custom_update_method)
               self.class.connection.write_lobs(self.class.table_name, self.class, attributes, @changed_lob_columns)