Fix UnboundLocalError and add environment detection debug

- Remove duplicate is_huggingface_space import in auth.py
- Add environment detection debugging in app.py
- This will show if HF Spaces detection is working
- Should fix the 500 error in auth callback

backend/app.py

@@ -61,6 +61,11 @@ session_secret = os.getenv("SESSION_SECRET_KEY") or secrets.token_urlsafe(32)
 
 # Detect if running in HF Spaces and adjust session config accordingly
 from utils.environment import is_huggingface_space
+
+# Debug environment detection
+logger.info(f"🔍 Environment detection: is_huggingface_space() = {is_huggingface_space()}")
+logger.info(f"🔍 SPACE_ID env var: {os.getenv('SPACE_ID')}")
+
 if is_huggingface_space():
     # HF Spaces optimized session configuration
     logger.info("🏗️ Configuring session middleware for HF Spaces environment")

backend/routers/auth.py

@@ -212,7 +212,6 @@ async def oauth_callback(request: Request, code: str, state: str):
             logger.error("❌ Session verification failed - user not found after saving")
         
         # Debug session state after saving
-        from utils.environment import is_huggingface_space
         if is_huggingface_space():
             session_keys = list(request.session.keys()) if hasattr(request.session, 'keys') else []
             logger.info(f"🔍 Auth callback - session keys after save: {session_keys}")