Score a custom feature vector

Third-party tools with their own probe data can score against Voidly's classifier. Body: {features: {anomaly_rate, measurement_count, spike_magnitude, day_of_week, month, is_weekend, rate_count_interaction, probe_block_rate, probe_node_count, probe_avg_confidence, probe_agreement, rate_spike_interaction, high_evidence}} matching the 13-feature v3.1 schema.