refactor(quickadapter): unify validation helpers with ValidationMode support
- Add ValidationMode type for "warn", "raise", "none" behavior
- Rename _UNSUPPORTED_CLUSTER_METRICS to _UNSUPPORTED_WEIGHTS_METRICS
- Refactor _validate_minkowski_p, _validate_quantile_q with mode support
- Add _validate_power_mean_p, _validate_metric_weights_support, _validate_label_weights
- Add _validate_enum_value for generic enum validation
- Add _prepare_knn_kwargs for sklearn-specific weight handling
- Remove deprecated _normalize_weights function
- Update all call sites to use new unified API