fix(accounting): 'Save & mark paid' actually pays; incoming invoices appear in tax/export

#1 Triage 'Save & mark paid' now marks the invoice paid directly (categorize +
   markInboundPaid with the entered reference) instead of opening the pay dialog
   and leaving it unpaid. Removed the PayModal chain.
#2 Cost side missed captured incoming invoices: the query required
   currency='CHF', but email/upload invoices often have a null currency →
   silently excluded. Now include null-currency rows (treated as the report
   currency). Also replaced COALESCE(invoice_date, created_at) with a split
   date filter (invoice_date BETWEEN, else created_at range) to avoid the
   mixed date/timestamp comparison risk on Postgres. Same fix in the ledger
   export (buildPostings).
en/de: categorizedPaidToast.

backend/src/services/ledgerService.js

@@ -297,10 +297,15 @@ async function buildPostings({ from, to, currency } = {}) {
         .modify((q) => {
           if (hasCatCol) q.leftJoin('expense_categories', 'inbound_documents.category_id', 'expense_categories.id');
         })
-        .whereRaw('COALESCE(inbound_documents.invoice_date, inbound_documents.created_at) >= ? AND COALESCE(inbound_documents.invoice_date, inbound_documents.created_at) <= ?', [from, toEnd])
-        .where('inbound_documents.currency', cur)
+        .where((qb) => {
+          qb.whereBetween('inbound_documents.invoice_date', [from, to])
+            .orWhere((q2) => q2.whereNull('inbound_documents.invoice_date')
+              .andWhere('inbound_documents.created_at', '>=', from)
+              .andWhere('inbound_documents.created_at', '<=', toEnd));
+        })
+        .where((qb) => { qb.where('inbound_documents.currency', cur).orWhereNull('inbound_documents.currency'); })
         .whereNotIn('inbound_documents.status', ['declined', 'duplicate'])
-        .orderByRaw('COALESCE(inbound_documents.invoice_date, inbound_documents.created_at) asc')
+        .orderBy('inbound_documents.created_at', 'asc')
         .select(
           'inbound_documents.id', 'inbound_documents.invoice_number', 'inbound_documents.invoice_date',
           'inbound_documents.created_at', 'inbound_documents.supplier_name', 'inbound_documents.tax_treatment',

backend/src/services/taxReportService.js

@@ -213,10 +213,21 @@ async function loadCosts({ from, to, cur }) {
   if (await db.schema.hasTable('inbound_documents')) {
     const inbound = await db('inbound_documents')
       .leftJoin('events', 'inbound_documents.event_id', 'events.id')
-      .whereRaw('COALESCE(inbound_documents.invoice_date, inbound_documents.created_at) >= ? AND COALESCE(inbound_documents.invoice_date, inbound_documents.created_at) <= ?', [from, toEnd])
-      .where('inbound_documents.currency', cur)
+      // Date in range: invoice_date (a DATE) when set, else created_at (a
+      // TIMESTAMP). Split instead of COALESCE so we never compare mixed
+      // date/timestamp types (a Postgres error the mocked tests can't see).
+      .where((qb) => {
+        qb.whereBetween('inbound_documents.invoice_date', [from, to])
+          .orWhere((q2) => q2.whereNull('inbound_documents.invoice_date')
+            .andWhere('inbound_documents.created_at', '>=', from)
+            .andWhere('inbound_documents.created_at', '<=', toEnd));
+      })
+      // Currency match, but INCLUDE rows with no currency set — captured
+      // invoices (email/upload) often have a null currency; treat them as the
+      // report currency rather than silently dropping them from the cost side.
+      .where((qb) => { qb.where('inbound_documents.currency', cur).orWhereNull('inbound_documents.currency'); })
       .whereNotIn('inbound_documents.status', ['declined', 'duplicate'])
-      .orderByRaw('COALESCE(inbound_documents.invoice_date, inbound_documents.created_at) asc')
+      .orderBy('inbound_documents.created_at', 'asc')
       .select(
         'inbound_documents.id',
         'inbound_documents.invoice_date',