Fix model path resolution to use correct project root

backend/ml/ml_engine.py

@@ -144,7 +144,7 @@ def _load_roberta(ckpt_path: str) -> bool:
 def init_models(psycho_model_dir: str, roberta_ckpt: str) -> None:
     global DEMO_MODE
     # Resolve relative paths from the project root (where app.py lives)
-    _root = os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+    _root = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
     if psycho_model_dir and not os.path.isabs(psycho_model_dir):
         psycho_model_dir = os.path.join(_root, psycho_model_dir)
     if roberta_ckpt and not os.path.isabs(roberta_ckpt):