fix: resolve NameError in get_current_user dependency causing 500 errors

app/dependencies.py

@@ -77,6 +77,15 @@ async def get_current_user(
             detail="Not authenticated",
             headers={"WWW-Authenticate": "Bearer"},
         )
+    
+    payload = decode_access_token(token)
+    if not payload:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid or expired token",
+            headers={"WWW-Authenticate": "Bearer"},
+        )
+
     return {
         "id": payload.get("sub"),
         "email": payload.get("email"),