- Extract PDO_OPTIONS constant for connection settings
- Add hasRecorders() helper to avoid repeated getRecorders() calls
- Add isSubquery() helper with safer regex pattern for subquery detection
- Add buildSelectQuery() to eliminate duplication between select() and selectIterator()
- Fix SQL syntax: replace LIMIT/OFFSET with DB2-compatible FETCH FIRST/OFFSET ROWS
- Refactor connect() to use array-based DSN building
- Standardize query logging with startQuery()/stopQuery() pattern
- Remove unused chunkSize parameter from fetchIterator()