Fix JSON serialization of numpy floats in ML predictions

backend/ml/ml_engine.py

@@ -309,11 +309,11 @@ def predict(
 
     return {
         "psycho_label":  psycho_label,
-        "psycho_score":  round(psycho_score, 4) if psycho_score is not None else None,
+        "psycho_score":  round(float(psycho_score), 4) if psycho_score is not None else None,
         "text_label":    text_label,
-        "text_score":    round(text_score, 4) if text_score is not None else None,
+        "text_score":    round(float(text_score), 4) if text_score is not None else None,
         "fused_label":   fused_label,
-        "fused_score":   round(fused_score, 4),
+        "fused_score":   round(float(fused_score), 4),
         "modality_used": modality_used,
     }