fix(accounting): address the-luap PR #636 review

- #1 resolveTaxTreatment: an unconfigured (empty) reclaim-countries list no
  longer auto-classifies every supplier — incl. the admin's own domestic one —
  as foreign; defer auto-classification until the setting is set (+ test).
- #2 pending re-bills on customer erase: eraseCustomer now returns the
  customer's not-yet-billed inbound docs to the inbox (null customer + unsorted)
  so they aren't billable to an anonymized account. (NB: picpeak has no hard
  customer delete — erase anonymizes in place — so the orphan/404 premise can't
  occur; this is hardening.)
- #4 VatRateSelect: when >1 configured code shares the same rate, fall through
  to the legacy "(not configured)" option instead of silently picking the first.
- #5 unwindBilledLine: delete the (mutable, never-issued) invoice when the
  unwound re-bill was its only line, instead of leaving a net-zero survivor.
- #6 isInvoiceMutable: clarify in a comment that invoices have no 'draft' status
  (the editable state is 'scheduled' w/o send-at) — no behaviour change.
- nit: collapse normalizeCurrency's tautological ternary.
- Fix VAT picker i18n: t('vat.legacyRate') → 'ledger.vat.legacyRate' (the key's
  real home), so the legacy label localizes instead of always showing English.
- Remove dead i18n keys left by the settings refactor (businessProfile.field VAT
  /hourly + profileFields.title/savedToast).

backend/src/services/customerAccountsService.js

@@ -785,6 +785,18 @@ async function eraseCustomer(id, erasedByAdminId) {
 
     // Active reset tokens for this customer should be invalidated.
     await trx('customer_password_resets').where('customer_account_id', id).del();
+
+    // Pending re-bills (incoming invoices, migration 132) attached to this
+    // customer would otherwise stay billable to the now-anonymized account —
+    // return the not-yet-billed ones to the inbox for re-triage so they're not
+    // silently lost or billed to a ghost (PR #636 review #2). Guarded for
+    // schema drift on installs that predate migration 132.
+    if (await trx.schema.hasColumn('inbound_documents', 'customer_account_id')) {
+      await trx('inbound_documents')
+        .where({ customer_account_id: id })
+        .whereNull('billed_invoice_id')
+        .update({ customer_account_id: null, disposition: null, status: 'unsorted', updated_at: new Date() });
+    }
   });
 
   await logActivity('customer_erased',

backend/src/services/expenseService.js

@@ -76,6 +76,10 @@ function resolveTaxTreatment(payloadTreatment, supplierCountry, reclaimCountries
   if (TAX_TREATMENTS.includes(payloadTreatment)) return payloadTreatment;
   const cc = String(supplierCountry || '').toUpperCase();
   if (!cc) return 'domestic';
+  // Don't auto-classify until the admin has actually configured their reclaim
+  // countries — an unset (empty) list must not make every supplier, including
+  // the admin's own domestic one, "foreign". (PR #636 review #1.)
+  if (!reclaimCountries || reclaimCountries.length === 0) return 'domestic';
   return reclaimCountries.includes(cc) ? 'domestic' : 'foreign_vat_non_reclaimable';
 }
 
@@ -287,6 +291,10 @@ const BOOKING_DISPOSITIONS = ['rebill', 'durchlaufend'];
 function isInvoiceMutable(invoice) {
   if (!invoice) return true; // referenced invoice gone — treat as not billed
   if (invoice.is_monthly_draft === true || invoice.is_monthly_draft === 1) return true;
+  // NB: invoices have no 'draft' status (only quotes do). The editable,
+  // not-yet-sent invoice state IS 'scheduled' with no scheduled_send_at (or a
+  // future one), handled below — so there is no plain-'draft' case to slot in
+  // here (PR #636 review #6).
   if (invoice.status !== 'scheduled') return false;
   if (!invoice.scheduled_send_at) return true;
   return new Date(invoice.scheduled_send_at).getTime() > Date.now();
@@ -312,6 +320,15 @@ async function unwindBilledLine(trx, doc) {
   }
   if (invoice) {
     const allItems = await trx('invoice_line_items').where({ invoice_id: invoice.id });
+    if (allItems.length === 0) {
+      // The unwound re-bill was the only line — a net-zero invoice has no reason
+      // to survive, and these would otherwise pile up over re-categorisations.
+      // It's mutable (checked above) and never issued, so delete it outright
+      // (PR #636 review #5). For a monthly draft this just means the next append
+      // re-creates one.
+      await trx('invoices').where({ id: invoice.id }).del();
+      return;
+    }
     let netMinor = 0;
     for (const li of allItems) {
       if (li.parent_line_item_id == null) netMinor += Number(li.line_total_minor || 0);