do inspect signature once (#6197)

Author: adhami3310

reflex/vars/base.py

@@ -1731,10 +1731,10 @@ def add(a: NumberVar, b: NumberVar):
     Returns:
         The decorated function.
     """
+    func_args = list(inspect.signature(func).parameters)
 
     @functools.wraps(func)
     def wrapper(*args: P.args, **kwargs: P.kwargs) -> Var[T]:
-        func_args = list(inspect.signature(func).parameters)
         args_vars = {
             func_args[i]: (LiteralVar.create(arg) if not isinstance(arg, Var) else arg)
             for i, arg in enumerate(args)