radi8og/monthly-balance-enquiry-app ? reverse-engineered prompt

Build me a Flutter app called MonoBal that helps track my bank balance and spending for just the current month.

I want to set a starting balance, add income and expenses, and see the total update right away. Let me edit or delete transactions, search by title, and filter by income or expenses. Please add category tags too, like food, rent, salary, and show them clearly on each item. I also want dark mode, currency selection for rupees, dollars, euros, and pounds, and all of that should remember itself after I close the app.

Please include monthly history for past months in a read only archive, a category breakdown chart, recurring monthly items like rent or salary, and the ability to export a month as CSV. I also need full backup and restore for all data. If possible, add Firebase login with email and Google, plus a simple biometric or PIN app lock so the financial data stays protected. If you need current package docs or setup details, look them up online.