Add Bengali translations for billing module strings

[nafisa45]

Overview:

◾ Added Bengali translations for missing billing module strings.
◾ Ensured all translations are contextually accurate and culturally appropriate.

Changes:

◾ Translated keys under billing.* to Bengali.
◾ Maintained placeholders like %strong% and ensured proper positioning in the Bengali translations.

Why This is Needed:

◾ Completes the localization for the Bengali language.
◾ Improves accessibility for Bengali-speaking users.

Testing:

◾ Reviewed translations for correctness and context.
◾ Checked for formatting and placeholder usage to prevent runtime issues.

Checklist:

Checklist

• All strings translated.
• Placeholders retained properly.
• Changes reviewed for accuracy.

[CLAassistant]

All committers have signed the CLA.

[jelveh]

Thank you @nafisa45 for your contribution. Could you look into the CLA before I can review and merge this PR?

[nafisa45]

Thank you @nafisa45 for your contribution. Could you look into the CLA before I can review and merge this PR?

Signed it

[jelveh]

AI is telling me this is a great translation! Thank you for your contribution. We now have full support for Bengali 😇