Fix/show correct monthly cost

[talhak55]

Problem:
Monthly costs were misleadingly calculated by mixing yearly costs (divided by 12) with actual monthly costs.

Fix:

• Separates pure monthly costs from yearly costs
• Calculates and shows monthly cost only from actual monthly entries

Changes:

• Updated cost calculation logic in [stats_calculations.php]
• Updated translation method to pass an array of variables
• Added subscription cards in [index.php]

Before

After

[ellite]

Hi! Thank you for the contribution.
This is intended behaviour.
It's not the sum of all the monthly subscriptions. It's the ammount you need to pay, on average, per month.

[talhak55]

Hi! Thank you for the contribution. This is intended behaviour. It's not the sum of all the monthly subscriptions. It's the ammount you need to pay, on average, per month.

I'm aware of that, which is why I added extra cards showing the actual monthly cost rather than the average across all subscriptions. This is especially useful when users add one or more yearly subscriptions and need to calculate their real monthly expenses. My PR improves the readability of the true monthly cost view.