Add a native option to hide decimals for whole-number prices

FluentCart should include a native price-display setting under Store Settings → Currency / Number Format to control how decimal places are displayed.

Suggested options:

• Always show two decimal places: 10.00
• Hide decimals only for whole-number prices: 10, while keeping 10.50
• Optionally trim all trailing zeros

This setting should apply consistently across the storefront, product pages, cart, checkout, customer dashboard, emails, receipts and PDF invoices.

At present, displaying 10€ instead of 10.00€ requires adding the following PHP filter:

add_filter('fluent_cart/hide_unnecessary_decimals', '__return_true');

This is a basic currency-formatting preference and should not require merchants to install a snippets plugin or maintain custom PHP code.

Additionally, in our testing the current filter changed a value such as 12.10€ into 12.1€, although the documentation suggests that meaningful decimal places should be preserved. The desired behaviour is:

• 10.00€ → 10€
• 10.50€ → 10.50€
• 12.10€ → 12.10€

A native selector would make the behaviour clearer, safer and more consistent for non-technical store owners, especially in European stores where currency-formatting conventions matter.