feat: Implement back up and sync

[TheMayhem6328]

Let's say I want to keep an offline copy of my transaction history in case I want to restore it if I lose my phone. Or maybe, let's say I have more than one phone and want to keep my transaction data in sync on both devices.

For said hypothetical circumstances, I believe that an option to back up such data would be convenient.

Exporting the data could be done in many formats, like let's say CSV data like:

Label	DateTime	Amount
Balance Update	2025-01-08T21:36:25+0000	200
Uttara North -> Farmgate	2025-01-08T21:38:17+0000	-50

And to sync the data, a cloud provider like Google Drive can be utilized, like how WhatsApp does it.

Thanks for reading my feature request :D

[raiyansarker]

I believe the card keeps the last 10 transactions, and this project is supposed to be totally offline. I don't think the community would like to accept the change given the usp is that the app doesn't connect to internet!