Error Handling for Password manager

Improved error handling in check_password function

I found that the check_password function lacked proper error handling for several cases:

When the password file did not exist, which would result in a FileNotFoundError.
When the specified aim was not found in the CSV file, which was not clearly communicated to the user.
When the aim was unspecified or empty, leading to potential undefined behavior.

To address these issues, I added:

A check to verify the existence of the password file before attempting to read it, with an appropriate error message if it does not exist.
A message to inform the user when no password is found for the specified aim.
An error message for cases where the aim is unspecified or empty.

These changes improve the check_password function.

Refactored code for Calculator + Error Handling

Added try-except blocks to handle ValueError exceptions for integer inputs and solving equations for x.
Modified the divide() function to check for division by zero and handle it with an appropriate error message.
Added input validation for non-positive integers in functions prime_number(), prime_factor(), and square_root().
Added input validation for invalid equations or no solutions found in the solve() function.
Added try-except blocks to handle ValueError and ZeroDivisionError exceptions in the convert_fractions_to() function.
Added input validation for invalid decimal numbers in the convert_decimals_to() function.
Added input validation for invalid percent values in the convert_percents_to() function.