container: hledger-flow: paypal-business: treat cash back rebate as expense reduction

NOTE: since no description is given for *which* tx receives the rebate,
manual intervention is required for per-subaccount calculations (either
with custom rules or calculating outside of flow).

container/src/hledger-flow/accounts/paypal-business/paypal-business-shared.rules

@@ -1,6 +1,6 @@
 # docker-finance | modern accounting for the power-user
 #
-# Copyright (C) 2021-2025 Aaron Fiore (Founder, Evergreen Crypto LLC)
+# Copyright (C) 2021-2026 Aaron Fiore (Founder, Evergreen Crypto LLC)
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -99,9 +99,10 @@ if %from_email [a-z0-9]
 if %direction ^IN$
   account2 income:paypal-business:%subaccount:%currency_
 
+# TODO: if a rebate is ever a non-fiat asset (e.g., BTC), reconcile the taxable event (cost-basis)
 if %direction ^IN$
 & %type ^Debit Card Cash Back Bonus$
-  account2 income:paypal-business:%subaccount:rebate:%currency_
+  account2 expenses:paypal-business:%subaccount:%type:%currency_
   comment type:%type, balance_impact:%balance_impact, status:%status_, to_email:%to_email, txid:%txid, direction:%direction, taxed_as:REBATE
 
 # All non-income considered capital contributions (use custom rules as needed)