fix(payments): creditor address per Swedbank TwnNm rule (Validex round 2) (#1508)

A present PstlAdr must carry TwnNm from November 2026 (PFH_222), so
BGNR-to-BGNR payments now carry no creditor address at all (rule 020
requires none there), IBAN-debited payments carry the supplier's town
(snapshotted as payee_city) plus Ctry SE, and the debtor address comes
from company settings, clearing the info-level rule 236 as well.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

supabase/migrations/20260810191118_supplier_payment_batch_items_payee_city.sql

@@ -0,0 +1,12 @@
+-- Swedbank MIG rule PFH_222 (Validex round 2, 2026-08-10): when a creditor
+-- postal address is present, TwnNm is mandatory from November 2026. IBAN-
+-- debited payments require the address (rule 237), so items snapshot the
+-- supplier's city at creation, same immutability rules as the other payee
+-- fields. Nullable: suppliers without a city keep working (BGNR-debited
+-- payments carry no creditor address at all).
+--
+-- pg-test: covered-by tests/pg/supplier-payment-batches.pg.test.ts
+ALTER TABLE public.supplier_payment_batch_items
+  ADD COLUMN payee_city text;
+
+NOTIFY pgrst, 'reload schema';