Shorten `maxScore`

[tklein1801]

Description

In this story, we aim to truncate the rating scores for stocks to make the data representation more concise. The maxScore will be rounded down to the nearest even number, while maintaining the same rating ratio to avoid any distortion of the value.

Acceptance Criteria

• Implement a function to round down maxScore to the nearest even number.
• Ensure that the rating ratio remains the same after the truncation of maxScore.
• Test the function with various maxScore values to ensure it works as expected.
• Apply the function to all existing stock rating scores in the frontend