feat(vat)!: remove VAT entirely from offers, orders and issued orders

Accounting rule: nabidky, objednavky (incl. confirmation PDF) and objednavky
vydane are NOT tax documents - VAT belongs only on invoices. Per user
decision this is a FULL removal including DB columns.

- migration: DROP orders.vat_rate/apply_vat, issued_orders.vat_rate/apply_vat,
  issued_order_items.vat_rate, quotations.vat_rate/apply_vat (applied to
  dev + test DBs)
- services: net-only totals everywhere (computeIssuedOrderTotals(items) ->
  {total}; enrichOrder/enrichQuotation net; per-currency list totals net)
- PDFs (offers, order confirmation, issued order): no VAT columns/summary,
  single 'Celkem bez DPH' / 'Total excl. VAT' total, note under totals:
  'Ceny jsou uvedeny bez DPH. DPH bude uctovano dle platnych predpisu.';
  duplicate Cena/Celkem column merged (desc width 56%); orders-pdf render
  extracted as exported renderOrderConfirmationHtml for testability
- frontend: Uplatnit DPH checkboxes, VAT selects and per-item VAT columns
  removed from OfferDetail/OrderDetail/IssuedOrderDetail/
  OrderConfirmationModal/ReceivedOrders manual-create; list footers read
  'Celkem bez DPH'; invoice-from-order prefill now takes the company default
  VAT (invoice decides its own VAT)
- tests: suites reworked to net math; new pdf-vat-note.test.ts pins the
  exact cs+en note text and VAT-free layout on all three PDFs

Invoices and received invoices keep their VAT handling unchanged.

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

src/admin/pages/OrderDetail.tsx

@@ -144,9 +144,10 @@ export default function OrderDetail() {
     return () => window.removeEventListener("beforeunload", handler);
   }, [isDirty]);
 
+  // NET only — received orders are not tax documents (no VAT on them).
   const totals = useMemo(() => {
-    if (!order?.items) return { subtotal: 0, vatAmount: 0, total: 0 };
-    const subtotal = order.items.reduce((sum, item) => {
+    if (!order?.items) return { total: 0 };
+    const total = order.items.reduce((sum, item) => {
       if (Number(item.is_included_in_total)) {
         return (
           sum + (Number(item.quantity) || 0) * (Number(item.unit_price) || 0)
@@ -154,10 +155,7 @@ export default function OrderDetail() {
       }
       return sum;
     }, 0);
-    const vatAmount = Number(order.apply_vat)
-      ? subtotal * ((Number(order.vat_rate) || 0) / 100)
-      : 0;
-    return { subtotal, vatAmount, total: subtotal + vatAmount };
+    return { total };
   }, [order]);
 
   const statusMutation = useApiMutation<{ status: string }, unknown>({
@@ -236,14 +234,12 @@ export default function OrderDetail() {
 
   const handleGenerateConfirmation = async (
     lang: string,
-    applyVat: boolean,
     customItems?: Array<{
       description: string;
       quantity: number;
       unit: string;
       unit_price: number;
       is_included_in_total: boolean;
-      vat_rate: number;
     }>,
   ) => {
     setConfirmationLoading(true);
@@ -253,7 +249,7 @@ export default function OrderDetail() {
         {
           method: "POST",
           headers: { "Content-Type": "application/json" },
-          body: JSON.stringify({ lang, applyVat, items: customItems }),
+          body: JSON.stringify({ lang, items: customItems }),
         },
       );
       if (!response.ok) {
@@ -625,7 +621,7 @@ export default function OrderDetail() {
           empty={<EmptyState title="Žádné položky." />}
         />
 
-        {/* Totals */}
+        {/* Totals (NET only — orders are not tax documents) */}
         <Box
           sx={{
             mt: 2,
@@ -636,30 +632,6 @@ export default function OrderDetail() {
             gap: 0.5,
           }}
         >
-          <Box sx={{ display: "flex", justifyContent: "space-between" }}>
-            <Typography variant="body2" color="text.secondary">
-              Mezisoučet:
-            </Typography>
-            <Typography
-              variant="body2"
-              sx={{ fontFamily: "'DM Mono', Menlo, monospace" }}
-            >
-              {formatCurrency(totals.subtotal, order.currency)}
-            </Typography>
-          </Box>
-          {Number(order.apply_vat) > 0 && (
-            <Box sx={{ display: "flex", justifyContent: "space-between" }}>
-              <Typography variant="body2" color="text.secondary">
-                DPH ({order.vat_rate}%):
-              </Typography>
-              <Typography
-                variant="body2"
-                sx={{ fontFamily: "'DM Mono', Menlo, monospace" }}
-              >
-                {formatCurrency(totals.vatAmount, order.currency)}
-              </Typography>
-            </Box>
-          )}
           <Box
             sx={{
               display: "flex",
@@ -671,7 +643,7 @@ export default function OrderDetail() {
             }}
           >
             <Typography variant="body2" sx={{ fontWeight: 700 }}>
-              Celkem k úhradě:
+              Celkem bez DPH:
             </Typography>
             <Typography
               variant="body2"
@@ -829,11 +801,8 @@ export default function OrderDetail() {
             unit: it.unit || "",
             unit_price: Number(it.unit_price) || 0,
             is_included_in_total: Number(it.is_included_in_total) !== 0,
-            vat_rate: Number(order.vat_rate) || 21,
           }))}
           orderNumber={order.order_number}
-          defaultVatRate={Number(order.vat_rate) || 21}
-          applyVat={!!order.apply_vat}
         />
       )}
     </PageEnter>