FR: Add transaction type as rule condition option (#790)

* Add transaction type condition filter for rules

Add ability to filter rules by transaction type (income, expense, transfer).
This allows users to create rules that differentiate between transactions
with the same name but different types.

- Add Rule::ConditionFilter::TransactionType with select dropdown
- Register in TransactionResource condition_filters
- Add tests for income, expense, and transfer filtering

Closes #373

* Address PR review feedback for transaction type filter

- Fix income filter to exclude transfers and investment_contribution
- Fix expense filter to include investment_contribution regardless of sign
- Add i18n for option and operator labels
- Add tests for edge cases (transfer inflows, investment contributions)

Logic now matches Transaction::Search#apply_type_filter for consistency.

app/models/rule/condition_filter/transaction_type.rb

@@ -0,0 +1,42 @@
+class Rule::ConditionFilter::TransactionType < Rule::ConditionFilter
+  # Transfer kinds matching Transaction#transfer? method
+  TRANSFER_KINDS = %w[funds_movement cc_payment loan_payment].freeze
+
+  def type
+    "select"
+  end
+
+  def options
+    [
+      [ I18n.t("rules.condition_filters.transaction_type.income"), "income" ],
+      [ I18n.t("rules.condition_filters.transaction_type.expense"), "expense" ],
+      [ I18n.t("rules.condition_filters.transaction_type.transfer"), "transfer" ]
+    ]
+  end
+
+  def operators
+    [ [ I18n.t("rules.condition_filters.transaction_type.equal_to"), "=" ] ]
+  end
+
+  def prepare(scope)
+    scope.with_entry
+  end
+
+  def apply(scope, operator, value)
+    # Logic matches Transaction::Search#apply_type_filter for consistency
+    case value
+    when "income"
+      # Negative amounts, excluding transfers and investment_contribution
+      scope.where("entries.amount < 0")
+           .where.not(kind: TRANSFER_KINDS + %w[investment_contribution])
+    when "expense"
+      # Positive amounts OR investment_contribution (regardless of sign), excluding transfers
+      scope.where("entries.amount >= 0 OR transactions.kind = 'investment_contribution'")
+           .where.not(kind: TRANSFER_KINDS)
+    when "transfer"
+      scope.where(kind: TRANSFER_KINDS)
+    else
+      scope
+    end
+  end
+end

app/models/rule/registry/transaction_resource.rb

@@ -7,6 +7,7 @@ class Rule::Registry::TransactionResource < Rule::Registry
     [
       Rule::ConditionFilter::TransactionName.new(rule),
       Rule::ConditionFilter::TransactionAmount.new(rule),
+      Rule::ConditionFilter::TransactionType.new(rule),
       Rule::ConditionFilter::TransactionMerchant.new(rule),
       Rule::ConditionFilter::TransactionCategory.new(rule),
       Rule::ConditionFilter::TransactionDetails.new(rule),