Add atr_sl_mult and atr_tp_mult parameters to _calc_labels_vectorized and generate_dataset_vectorized, defaulting to existing constants (1.5, 2.0) for full backward compatibility. Callers (train scripts, backtester) can now pass symbol-specific multipliers without modifying module-level constants. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>