Create a Python program that consists of a single class named 'TemperatureConverter' in a file named 'temperature_converter.py'. The class should have the following methods:

- celsius_to_fahrenheit(self, celsius: float) -> float: Converts Celsius temperature to Fahrenheit.
- fahrenheit_to_celsius(self, fahrenheit: float) -> float: Converts Fahrenheit temperature to Celsius.

Create a separate 'main.py' file that imports the 'TemperatureConverter' class, takes user input for the temperature value and the unit, converts the temperature to the other unit, and then prints the result.