[2.2.1] Extend CSV Import / Export to support transfers

It would be great to be able to import / export transfers, not just transactions.

[Note from Fabian]

A few options I've been thinking about:

A) Using source/target accounts (like in MoneyWiz) [Current Favorite]:

• This would match two transactions as a transfer based on similar attributes (e.g. same notes, date, inverted amount, etc.). However, this gets tricky when amounts don't match exactly — for example, if transfer fees are involved. Budget Flow allows editing each side of a transfer independently to reflect real-world differences.

• One idea could be to only create a link if it's a clean 1:1 match — anything else would be skipped or simply not linked and only set to "Not evaluated".

B) Using a unique Transfer ID:

• Each transfer in the CSV could optionally include a shared ID that links the two related transactions together, no matter the other details. This would give users full control. However it might not be as user friendly and confusing to assign unique IDs by hand.

C) Adding an "Evaluated" column to the CSV:

• This wouldn't link transfers, but at least it would prevent them from skewing the insights and reports.

[Optional] Automatically set all Transactions which are assigned to a “Transfer” category as “Not Evaluated” (like in MoneyCoach)

Also add a column where you can specify whether a transaction is “Pending” or not.

CSV-Extension (Summary):

• Rename Column “Account” to “Source Account”

• Add Column “Target Account” (Optional; Necessary For Transfers)

• Add Column “Pending” (Optional; Useful For Credit Cards)

• Add Special Handling for some CSV Files

  • If Category = “Transfer” then set evaluated to false by default