feat: Redesign Transaction start date flow

[marination]

Working:

• For the first setup (no Bank with consent details/no Kosma fetched Bank), a prompt for a start date will appear
• This start date will be used to generate the first consent token, so that the first transactions fetch will happen from this start date to the current date
• After Bank creation, the consent start date is registered as the start date given by the user

When the consent is regenerated in the future, a start date will not be asked. That is a one time prompt. The consent start date will be the current fiscal year

• Transactions are auto fetched every day. The fetch is resumed from the Last Integration Date in the Bank Account
• In case you want to fetch transactions from some particular time period you can, by clicking Sync > Older Transactions. Authentication will be required for this:

ToDos:

• [x] Ask user for start date the first time setup is done (consent will store this date as the start date for transactions)
• [x] Transactions fetch must use consent start date if no last integration date in account.
• [x] Flow API for adhoc fetching of transactions from a particular date or any time period

[marination]

@barredterra don't merge this. I think i fixed fetching older transactions too

[marination]

Flow API for adhoc fetching of transactions needs more testing with other bank accounts. The rest looks fine. Merging.