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/__tests__/schema-nan.test.ts

@@ -58,34 +58,6 @@ describe("Zod form coercion + NaN rejection", () => {
   });
 
   describe("CreateQuotationSchema", () => {
-    it("rejects NaN string in top-level vat_rate", () => {
-      const result = CreateQuotationSchema.safeParse({
-        customer_id: 1,
-        vat_rate: "bad",
-      });
-      expect(result.success).toBe(false);
-    });
-
-    it("accepts valid vat_rate", () => {
-      const result = CreateQuotationSchema.safeParse({
-        customer_id: 1,
-        vat_rate: 21,
-      });
-      expect(result.success).toBe(true);
-    });
-
-    it("coerces a valid numeric STRING vat_rate to a number", () => {
-      const result = CreateQuotationSchema.safeParse({
-        customer_id: 1,
-        vat_rate: "21",
-      });
-      expect(result.success).toBe(true);
-      if (result.success) {
-        expect(result.data.vat_rate).toBe(21);
-        expect(typeof result.data.vat_rate).toBe("number");
-      }
-    });
-
     it("rejects NaN string in item quantity", () => {
       const result = CreateQuotationSchema.safeParse({
         customer_id: 1,
@@ -300,8 +272,8 @@ describe("schema hardening — does not reject previously-valid input", () => {
     expect(b.success).toBe(true);
     if (b.success) expect(b.data.trip_date).toBe("2026-06-09");
     // Genuinely malformed dates are still rejected.
-    expect(CreateTripSchema.safeParse({ ...base, trip_date: "09/06/2026" }).success).toBe(
-      false,
-    );
+    expect(
+      CreateTripSchema.safeParse({ ...base, trip_date: "09/06/2026" }).success,
+    ).toBe(false);
   });
 });