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/schemas/issued-orders.schema.ts

@@ -1,10 +1,8 @@
 import { z } from "zod";
 import {
-  numberInRange,
   nonNegativeNumberFromForm,
   positiveNumberFromForm,
   nullableIntIdFromForm,
-  booleanFromForm,
   isoDateString,
 } from "./common";
 
@@ -14,7 +12,6 @@ export const IssuedOrderItemSchema = z.object({
   quantity: positiveNumberFromForm.optional(),
   unit: z.string().max(20).nullish(),
   unit_price: nonNegativeNumberFromForm.optional(),
-  vat_rate: numberInRange(0, 100).optional(),
   position: z.number().int().nonnegative().optional(),
 });
 
@@ -31,8 +28,6 @@ export const CreateIssuedOrderSchema = z.object({
   supplier_id: nullableIntIdFromForm.nullish(),
   status: z.enum(ISSUED_ORDER_STATUSES).optional(),
   currency: z.string().max(10).optional(),
-  vat_rate: numberInRange(0, 100).optional(),
-  apply_vat: booleanFromForm.optional(),
   exchange_rate: nonNegativeNumberFromForm.optional(),
   order_date: isoDateString.nullish(),
   delivery_date: isoDateString.nullish(),