Don't import duplicate transactions

[bkakilli]

Describe the feature

maybe can hash fields (especially date+amount) together and skip duplicates when importing new data. This could be an optional setting on the import menu.

Why is this feature important?

When importing transactions from a bank CSV maybe does not check if there are duplicates already imported. If there is a time range overlap with a previous import, we would end up importing a portion of the transactions twice.

I think currently the only viable way to add transactions is through import. Without this feature the user must manually keep track of the exact times of their imports, so that the new ones won't coincide with the earlier ones. This is a huge burden and prone to human mistakes.

Additional context, screenshots, and relevant links

No response