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/OfferDetail.tsx

@@ -118,8 +118,6 @@ interface OfferForm {
   valid_until: string;
   currency: string;
   language: string;
-  vat_rate: number;
-  apply_vat: boolean;
 }
 
 const emptyForm: OfferForm = {
@@ -131,8 +129,6 @@ const emptyForm: OfferForm = {
   valid_until: "",
   currency: "CZK",
   language: "EN",
-  vat_rate: 21,
-  apply_vat: false,
 };
 
 const emptyScopeSection = (): ScopeSection => ({
@@ -585,10 +581,6 @@ export default function OfferDetail() {
           prev.currency === "CZK"
             ? companySettings.default_currency || "CZK"
             : prev.currency,
-        vat_rate:
-          prev.vat_rate === 21
-            ? (companySettings.default_vat_rate ?? 21)
-            : prev.vat_rate,
       }));
     }
   }, [companySettings, isEdit]);
@@ -639,8 +631,6 @@ export default function OfferDetail() {
       valid_until: d.valid_until ? d.valid_until.substring(0, 10) : "",
       currency: d.currency || companySettings?.default_currency || "CZK",
       language: d.language || "EN",
-      vat_rate: d.vat_rate ?? companySettings?.default_vat_rate ?? 21,
-      apply_vat: !!d.apply_vat,
     };
     setForm(formData);
     const mappedItems =
@@ -790,7 +780,8 @@ export default function OfferDetail() {
     setItems((prev) => prev.filter((_, i) => i !== index));
   };
 
-  const subtotal = items.reduce((sum, item) => {
+  // NET only — offers are not tax documents (no VAT on them).
+  const total = items.reduce((sum, item) => {
     if (item.is_included_in_total) {
       return (
         sum + (Number(item.quantity) || 0) * (Number(item.unit_price) || 0)
@@ -798,8 +789,6 @@ export default function OfferDetail() {
     }
     return sum;
   }, 0);
-  const vatAmount = form.apply_vat ? subtotal * (form.vat_rate / 100) : 0;
-  const total = subtotal + vatAmount;
 
   const handleSave = async (targetStatus?: string) => {
     const newErrors: Record<string, string> = {};
@@ -1389,44 +1378,6 @@ export default function OfferDetail() {
             />
           </Field>
         </Box>
-
-        <Box
-          sx={{
-            display: "grid",
-            gridTemplateColumns: { xs: "1fr", md: "1fr 1fr 1fr" },
-            gap: 2,
-          }}
-        >
-          <Field label="Sazba DPH">
-            <Box sx={{ display: "flex", gap: 1, alignItems: "center" }}>
-              <Select
-                value={String(form.vat_rate)}
-                onChange={(val) => updateForm("vat_rate", parseFloat(val) || 0)}
-                disabled={readOnly}
-                sx={{ flex: 1 }}
-                options={(
-                  companySettings?.available_vat_rates || [0, 10, 12, 15, 21]
-                ).map((r) => ({ value: String(r), label: `${r}%` }))}
-              />
-              <Box
-                component="label"
-                sx={{
-                  display: "flex",
-                  alignItems: "center",
-                  whiteSpace: "nowrap",
-                  cursor: readOnly ? "default" : "pointer",
-                }}
-              >
-                <Checkbox
-                  checked={form.apply_vat}
-                  onChange={(e) => updateForm("apply_vat", e.target.checked)}
-                  disabled={readOnly}
-                />
-                <Box component="span">Uplatnit DPH</Box>
-              </Box>
-            </Box>
-          </Field>
-        </Box>
       </Card>
 
       {/* Items Section with drag-and-drop */}
@@ -1596,7 +1547,7 @@ export default function OfferDetail() {
           </SortableContext>
         </DndContext>
 
-        {/* Totals */}
+        {/* Totals (NET only — offers are not tax documents) */}
         <Box
           sx={{
             mt: 2,
@@ -1607,30 +1558,6 @@ export default function OfferDetail() {
             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(subtotal, form.currency)}
-            </Typography>
-          </Box>
-          {form.apply_vat && (
-            <Box sx={{ display: "flex", justifyContent: "space-between" }}>
-              <Typography variant="body2" color="text.secondary">
-                DPH ({form.vat_rate}%):
-              </Typography>
-              <Typography
-                variant="body2"
-                sx={{ fontFamily: "'DM Mono', Menlo, monospace" }}
-              >
-                {formatCurrency(vatAmount, form.currency)}
-              </Typography>
-            </Box>
-          )}
           <Box
             sx={{
               display: "flex",
@@ -1642,7 +1569,7 @@ export default function OfferDetail() {
             }}
           >
             <Typography variant="body2" sx={{ fontWeight: 700 }}>
-              Celkem:
+              Celkem bez DPH:
             </Typography>
             <Typography
               variant="body2"