Isolated Apps / Dynamic Budgets followup tasks

From https://github.com/getAlby/hub/pull/226

- [ ] mixing DB transactions with "payment transactions" is not so good
- [x] Enable Roman's cleanup task for old request and response events
- [ ] isolated app possible follow-ups (in case we wish to spend more time on isolated apps)
- [x] internal payments should trigger NIP-47 notifications (this can be done by the transactions service publishing its own notifications rather than the notifier subscribing to LNClient notifications - this would simplify things too)
- restrict isolated balance to not receive more than a certain budget (it's hard to do?)
- prevent hub not spending balance that is set aside for other apps
- prevent paying more than actual balance from main wallet into isolated wallets (you can send an infinite amount)
- cashu isolated app payments does not work and causes money to be "lost" - disabled for now
- [x] currently there are no DB indexes. I am not sure how this will perform when the number of payments grow
- [ ] ListTransactions on LNClients that support notifications should actually just throw an error (they should never be used)
- [x] LDK
- [ ] LND
- [x] fee reserve calculation could be per-LNClient to completely match what the node sets - now fee reserve is same for both LND and LDK
- [ ] Extra nip-47 controller tests
- [x] multi_pay_keysend (partial success)
- [x] list_transactions (paging params)
- [x] onboard your friend/family flow with Dynamic Budgets and Alby Mobile
- [x] undo LDK database changes in Alby fork (probably by undoing changes and then deleting old payments in a migration as they will be unused after we have our own payment DB)
- [x] Blog post