retire the bunq integration

The webhook is deregistered at bunq and the callback endpoint, its parser,
default-deny classifier, dedup ledger and signature check are removed; the
code is in git history if a bank feed ever comes back. /financials keeps
reading the hand-maintained aggregates file, and sales + shop donations
stay live from the order ledger.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

shared/interfaces/Catcrafts.Shared-Content.cppm

@@ -246,7 +246,7 @@ export const LegalPage& FinancialsPage() {
         .sections = {
             { "How this page works",
               {
-                  "Sales, and donations made through the shop, come straight from the shop's order ledger and update the moment they are paid. Donations to the bank account and expenses are aggregated from the business bank account by category and carry the date they were last brought up to date. Anything the categoriser does not recognise is held back until it has been classified, never published as a guess.",
+                  "Sales, and donations made through the shop, come straight from the shop's order ledger and update the moment they are paid. Donations to the bank account and expenses are aggregated from the business bank account by category, brought up to date by hand, and carry the date that last happened.",
                   "Everything is a running total in euros on a cash basis: money counts when it moves, not when an invoice says it should. Amounts include VAT where VAT was charged.",
               } },
             { "What is never published",