fix: refuse unavailable gallery and pin head trainer

recognization/code/finetune_identity.py

@@ -132,12 +132,14 @@ def enrollment_report_text(report: dict) -> str:
 
 
 def build_model(image_size: int = 518):
-    import timm
     import torch
 
+    from gallery import load_dinov2
+
     device = "mps" if torch.backends.mps.is_available() else "cpu"
-    model = timm.create_model("vit_small_patch14_dinov2.lvd142m", pretrained=True,
-                              num_classes=0, img_size=image_size, dynamic_img_size=True)
+    # Same hash-pinned local file as inference. pretrained=True would fetch a
+    # different copy even with YOLO_OFFLINE=1.
+    model = load_dinov2(image_size)
     return model.eval().to(device), device