Feature Request: Filter transactions with no merchant assigned

[twisterniq]

Describe the feature

On the Transactions page, add a "No merchant" option to the Merchant filter, showing only transactions that have no merchant assigned — similar to how "Uncategorized" already works for categories.

Ideally it should be combinable with other filters (date range, account, amount), like the existing merchant filter is.

Why is this feature important?

Merchants are typically assigned gradually over time (manually or via rules), so a very common workflow is cleanup: finding everything that has not been organized yet.

Right now there is no way to answer "which transactions do not have a merchant assigned yet?" other than going through the list manually, which does not scale once you have thousands of transactions. Since categories already offer this via "Uncategorized", extending the same idea to merchants would feel consistent and cover a real gap in transaction hygiene workflows.

Additional context

• Related discussion about negative matching in rules: Feature Request: Support for more robust filters, including negative filters (!contains or !=) & AND/OR nesting, #530
• This request is about the transactions page filter UI, not the rules engine.