feat(accounting): VAT-code dropdown in the quote editor (+ reusable VatRateSelect)

Slice 3a — replaces the free-typed VAT rate in the quote editor with a dropdown
of configured output VAT codes (+ 'Other (custom rate)'), reading the un-gated
/admin/vat-codes endpoint. Selecting a code sends vatCode → the backend snapshots
it (migration 130) and the export emits it. New VatRateSelect component + a
read-only vatCodes.service. Create flow snapshots correctly; loading a saved code
into the editor (serialization return) + the bill editor are the next slices.
Build green.

frontend/src/components/admin/VatRateSelect.tsx

@@ -0,0 +1,77 @@
+/**
+ * VAT-rate picker for the invoice/quote editors. A dropdown of the configured
+ * OUTPUT VAT codes (Settings → Accounting) plus an "Other (custom rate)" escape
+ * hatch. Controlled by `(rate, code)`: selecting a code emits its rate + code
+ * string (snapshotted on the document for the accounting export); "Other" emits
+ * the typed rate with a null code. Reads the un-gated /admin/vat-codes endpoint,
+ * so it works even when the accounting feature is off.
+ */
+import React from 'react';
+import { useQuery } from '@tanstack/react-query';
+import { useTranslation } from 'react-i18next';
+import { vatCodesService, type VatCodeOption } from '../../services/vatCodes.service';
+
+const CUSTOM = '__custom__';
+const selectCls =
+  'w-full rounded-md border border-neutral-300 dark:border-neutral-600 bg-white dark:bg-neutral-800 px-3 py-2 text-sm text-neutral-900 dark:text-neutral-100 focus:outline-none focus:ring-2 focus:ring-primary-500';
+
+interface Props {
+  rate: number;
+  code: string | null;
+  onChange: (rate: number, code: string | null) => void;
+  label?: string;
+  disabled?: boolean;
+}
+
+export const VatRateSelect: React.FC<Props> = ({ rate, code, onChange, label, disabled }) => {
+  const { t } = useTranslation();
+  const { data: codes = [] } = useQuery({
+    queryKey: ['vat-codes', 'output'],
+    queryFn: () => vatCodesService.listOutput(),
+    staleTime: 5 * 60 * 1000,
+  });
+
+  // Selected option: prefer the snapshotted code; else a code whose rate matches
+  // (legacy rows / no code stored); else "custom".
+  const matched: VatCodeOption | undefined =
+    (code ? codes.find((c) => c.code === code) : undefined)
+    || (!code ? codes.find((c) => Number(c.rate) === Number(rate)) : undefined);
+  const isCustom = !matched;
+
+  return (
+    <div>
+      {label && (
+        <label className="block text-sm font-medium text-neutral-700 dark:text-neutral-300 mb-1">{label}</label>
+      )}
+      <select
+        className={selectCls}
+        disabled={disabled}
+        value={isCustom ? CUSTOM : String(matched!.id)}
+        onChange={(e) => {
+          if (e.target.value === CUSTOM) { onChange(rate, null); return; }
+          const c = codes.find((x) => String(x.id) === e.target.value);
+          if (c) onChange(Number(c.rate), c.code);
+        }}
+      >
+        {codes.map((c) => (
+          <option key={c.id} value={String(c.id)}>
+            {c.name} ({Number(c.rate).toFixed(1)}%)
+          </option>
+        ))}
+        <option value={CUSTOM}>{t('vat.customRate', 'Other (custom rate)')}</option>
+      </select>
+      {isCustom && (
+        <input
+          type="number"
+          step="0.1"
+          min="0"
+          className={`${selectCls} mt-2`}
+          disabled={disabled}
+          value={rate}
+          placeholder={t('vat.ratePercent', 'VAT rate %') as string}
+          onChange={(e) => onChange(Number(e.target.value) || 0, null)}
+        />
+      )}
+    </div>
+  );
+};

frontend/src/pages/admin/quotes/QuoteEditorPage.tsx

@@ -25,6 +25,7 @@ import {
 import { LineItemsTable, type EditableLineItem } from '../../../components/admin/LineItemsTable';
 import { CustomerPicker } from '../../../components/admin/CustomerPicker';
 import { ProjectSelect } from '../../../components/admin/ProjectSelect';
+import { VatRateSelect } from '../../../components/admin/VatRateSelect';
 import { InstallmentsPanel } from '../../../components/admin/InstallmentsPanel';
 import { customerAdminService } from '../../../services/customerAdmin.service';
 import { userManagementService } from '../../../services/userManagement.service';
@@ -54,6 +55,8 @@ interface FormState {
   paymentNetDaysTemplateId: number | null;
   paymentTimingTemplateId: number | null;
   vatRate: number;
+  /** Migration 130 — snapshot of the chosen output VAT code (null = custom rate). */
+  vatCode: string | null;
   shippingAmount: number;
   introText: string;
   outroText: string;
@@ -85,6 +88,7 @@ const empty: FormState = {
   paymentNetDaysTemplateId: null,
   paymentTimingTemplateId: null,
   vatRate: 0,
+  vatCode: null,
   shippingAmount: 0,
   introText: '',
   outroText: '',
@@ -121,6 +125,7 @@ function buildPayload(f: FormState): QuoteCreatePayload {
     // installments on the snapshot. Sent only when populated.
     installments: f.installments && f.installments.length > 0 ? f.installments : undefined,
     vatRate: f.vatRate,
+    vatCode: f.vatCode,
     shippingAmountMinor: toMinor(f.shippingAmount),
     introText: f.introText || undefined,
     outroText: f.outroText || undefined,
@@ -214,6 +219,7 @@ export const QuoteEditorPage: React.FC = () => {
         paymentNetDaysTemplateId: q.paymentNetDaysTemplateId,
         paymentTimingTemplateId: q.paymentTimingTemplateId,
         vatRate: Number(q.vatRate || 0),
+        vatCode: (q as { vatCode?: string | null }).vatCode ?? null,
         shippingAmount: Number(q.shippingAmountMinor || 0) / 100,
         introText: q.introText || '',
         outroText: q.outroText || '',
@@ -533,9 +539,11 @@ export const QuoteEditorPage: React.FC = () => {
           onChange={(items) => setForm((f) => ({ ...f, lineItems: items }))}
         />
         <div className="grid grid-cols-1 md:grid-cols-3 gap-3 mt-4">
-          <Input type="number" step="0.1" label={t('quotes.field.vatRate', 'VAT rate %') as string}
+          <VatRateSelect
-            value={form.vatRate}
+            label={t('quotes.field.vatRate', 'VAT rate %') as string}
-            onChange={(e) => setForm((f) => ({ ...f, vatRate: Number(e.target.value) }))} />
+            rate={form.vatRate}
+            code={form.vatCode}
+            onChange={(rate, code) => setForm((f) => ({ ...f, vatRate: rate, vatCode: code }))} />
           <Input type="number" step="0.01" label={t('quotes.field.shipping', 'Shipping amount') as string}
             value={form.shippingAmount}
             onChange={(e) => setForm((f) => ({ ...f, shippingAmount: Number(e.target.value) }))} />

frontend/src/services/quotes.service.ts

@@ -191,6 +191,8 @@ export interface QuoteCreatePayload {
    *  the template's value as-is. */
   installments?: PaymentTermInstallment[];
   vatRate?: number;
+  /** Migration 130 — snapshot of the chosen output VAT code (null = custom rate). */
+  vatCode?: string | null;
   shippingAmountMinor?: number;
   introText?: string;
   outroText?: string;

frontend/src/services/vatCodes.service.ts

@@ -0,0 +1,21 @@
+/**
+ * Read-only VAT-code registry for the invoice/quote editors. Hits the un-gated
+ * /admin/vat-codes endpoint (works without the accounting feature). Management
+ * lives in Settings → Accounting (ledger.service).
+ */
+import { api } from '../config/api';
+
+export interface VatCodeOption {
+  id: number;
+  code: string;
+  name: string;
+  rate: number;
+  direction: 'output' | 'input';
+}
+
+export const vatCodesService = {
+  async listOutput(): Promise<VatCodeOption[]> {
+    const { data } = await api.get('/admin/vat-codes', { params: { direction: 'output' } });
+    return (data?.items ?? []) as VatCodeOption[];
+  },
+};