fix(bookkeeping): settle öre differences to 3740 and improve supplier-invoice matching (#699)

Whole-krona Bankgiro/Swish payments of öre-bearing invoices were stranded
as partially_paid forever (e.g. 11 231 paid on an 11 231,25 invoice left
0,25 kr open). Book the sub-krona residual to BAS 3740 (Öres- och
kronutjämning) and settle the invoice in full, on both the supplier- and
customer-invoice match flows.

New shared pure helpers buildSupplierPaymentClearingLines +
planSupplierPayment mirror the customer-side primitives; routing preview
and commit through the same builder also fixes two pre-existing
preview↔commit drifts (payment account + line descriptions). Öre
absorption is accrual-only — cash entries book the full invoice, so
absorbing there would hide a 1930 discrepancy.

Also improves supplier-invoice ↔ bank matching:
- Pass-3 date window now spans [invoice_date-5, due_date+5] instead of
  due_date ±5, so early payments auto-match; an ambiguity guard demotes
  non-unique amount matches to suggestions.
- New retroactive matcher (on supplier_invoice.registered/.approved)
  surfaces the settling bank payment when the invoice is registered after
  the payment was imported. Matches are written as suggestions for
  one-click confirm-to-book, never silently auto-booked.

Tests: new unit tests for both pure helpers; extended matching, handler,
customer öre, and route suites. Full suite green (407 files / 5364 tests).

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

messages/en.json

@@ -1826,6 +1826,7 @@
     "amount_diff": "Difference: {amount}",
     "different_currencies": " (different currencies)",
     "partial_payment_note": " — the invoice will become partially paid.",
+    "ore_rounding_note": "The {amount} difference is booked as rounding (account 3740). The invoice is marked as paid.",
     "fx_title": "Currency conversion",
     "fx_rate_description": "Riksbanken mid-rate {date}: 1 {invoiceCurrency} = {rate} SEK",
     "fx_paid_in_invoice_currency": "Payment equals: {amount}",

messages/sv.json

@@ -1826,6 +1826,7 @@
     "amount_diff": "Differens: {amount}",
     "different_currencies": " (olika valutor)",
     "partial_payment_note": " — fakturan blir delbetald.",
+    "ore_rounding_note": "Differens {amount} bokförs som öresavrundning (konto 3740). Fakturan markeras som betald.",
     "fx_title": "Valutaomräkning",
     "fx_rate_description": "Riksbankens mittkurs {date}: 1 {invoiceCurrency} = {rate} SEK",
     "fx_paid_in_invoice_currency": "Inbetalning motsvarar: {amount}",