Fix backend client initialization (lazy loading)

app.py

@@ -8,12 +8,18 @@ from gradio_client import Client
 from huggingface_hub import login
 import os
 
-# Authenticate and connect to protected backend
-HF_TOKEN = os.getenv("HF_TOKEN")
-if HF_TOKEN:
-    login(token=HF_TOKEN)
+# Global backend client
+backend = None
 
-backend = Client("rg321/Construction_Material_Classification")
+def get_backend():
+    """Lazy initialization of backend client"""
+    global backend
+    if backend is None:
+        HF_TOKEN = os.getenv("HF_TOKEN")
+        if HF_TOKEN:
+            login(token=HF_TOKEN)
+        backend = Client("rg321/Construction_Material_Classification")
+    return backend
 
 
 def classify_material(image):
@@ -25,7 +31,8 @@ def classify_material(image):
         print(f"📤 Calling backend API with image type: {type(image)}")
 
         # Call protected space API
-        result = backend.predict(image=image, api_name="/classify_material")
+        client = get_backend()
+        result = client.predict(image=image, api_name="/classify_material")
 
         print(f"📥 Backend response: {result}")