[bisq-network/bisq] Recurring offers to support dollar cost averaging (DCA) use cases (#5165)

[Max Hillebrand]

100% Concept ACK! A much requested and useful feature!

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## Challenges
### Privacy
> Assuming the offer gets taken, a new offer with the same details will be created on the 1st of the following month.

Notice that when the offer details are exactly the same, then there can be some fingerprinting and clustering of recurring offers of one users [at least for offerbook watchers]. For example, if exactly `123 USD` are always offered on the `4th` of every month, then an outside observer has a good guess that this is the same user.
Fwiw, such a clustering can be achieved with other attack vectors too, but automated recurring offers might worsen this threat.

A potential solution is to randomize the offer details within user input range, to something more vague like:
- Between the 1st and 7th of every month;
- offer to buy between 200 and 300 USD;
- at 0.5-1% above market rate.

[yeah, range user input sucks, so maybe make it optional]

### Non-automated fiat bank payments
One of the nice use cases of custodial DCA, is that the fiat bank transfer can be automated as recurring send **to the same receiver** [the exchange bank account]. This means BOTH the fiat transaction AND the bitcoin purchase are automated.

I understand how Bisq can automate the bitcoin purchase, but how can we automate the fiat bank transaction **to multiple different counter parties**? It seems to me that the user still has to become active for every trade, at least to get the trading-partners bank information and beg the bank for permission to do the transaction.

On the other hand, Bisq CAN automate fiat transactions when fiat certificates [like Tether] are managed within the Bisq wallet. So a potential workaround to the problem:
- First user exchanges fiat bank transfer for fiat certificates.
- Now user sets-up a recurring offer to trade fiat certificates for bitcoin.

Downsides to this approach is the upfront capital liquidity in fiat bank shitcoins. If the user does not have much fiat in the bank account, but he is receiving incoming cash flow regularly, from which he wants to make his bitcoin savings, then he still has to manually make the bank transfer recurringly. 

## Future direction
### Buy the dip automation
Add a new recurring offer condition:
- If bitcoin price drops X%;
- offer to buy Y USD;
- at Z % above market price.

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