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/orders.schema.ts

@@ -1,7 +1,6 @@
 import { z } from "zod";
 import {
   numberFromForm,
-  numberInRange,
   nonNegativeNumberFromForm,
   positiveNumberFromForm,
   intIdFromForm,
@@ -42,8 +41,6 @@ export const CreateOrderSchema = z.object({
     .default("prijata"),
   currency: z.string().max(20).optional().default("CZK"),
   language: z.string().max(20).optional().default("cs"),
-  vat_rate: numberInRange(0, 100).optional().default(21.0),
-  apply_vat: booleanFromForm.optional().default(true),
   exchange_rate: positiveNumberFromForm.optional().default(1.0),
   scope_title: z.string().max(255).nullish(),
   scope_description: z.string().max(8000).nullish(),
@@ -62,8 +59,6 @@ export const UpdateOrderSchema = z.object({
   scope_description: z.string().max(8000).nullish(),
   notes: z.string().max(8000).nullish(),
   customer_id: nullableIntIdFromForm.optional(),
-  vat_rate: numberInRange(0, 100).optional(),
-  apply_vat: booleanFromForm.optional(),
   items: z.array(OrderItemSchema).optional(),
   sections: z.array(OrderSectionSchema).optional(),
 });