feat(accounting): Accounting nav section + relocate Tax report out of CRM

Adds the `accounting` feature flag to the frontend (type, context default) and
a Settings -> Features toggle card. When enabled:

- A new top-level "Accounting" sidebar entry appears (gated by `accounting` +
  accounting.view), with an AccountingLayout sub-nav mirroring ClientsLayout.
- The Tax report relocates: it is HIDDEN from the CRM (Clients) sub-nav and
  shown under Accounting instead, at /admin/accounting/tax-report. When
  accounting is OFF, Tax stays under CRM exactly as before.

Tax visibility still depends on `taxReport` (which depends on `bills`), so the
relocation only changes WHERE the menu item lives, not whether it exists.

Files: featureFlags.service.ts (+'accounting'), FeatureFlagsContext default,
AdminSidebar entry, new AccountingLayout, ClientsLayout filter, App.tsx route,
FeaturesTab card, en/de i18n (navigation.accounting, accounting.*,
settings.features.accounting; DE authored natively).

Verified: `npm run build` green; en/de JSON valid.

frontend/src/App.tsx

@@ -64,6 +64,7 @@ import {
 import { CustomerAuthProvider } from './contexts/CustomerAuthContext';
 import { AdminLayout, AdminAuthWrapper } from './components/admin';
 import { ClientsLayout } from './components/admin/ClientsLayout';
+import { AccountingLayout } from './components/admin/AccountingLayout';
 import { RequireFeature } from './components/admin/RequireFeature';
 import { PageErrorBoundary, OfflineIndicator, SkipLink, DynamicFavicon, RobotsMetaTags, CMSContentBlock, Loading } from './components/common';
 import { MaintenanceWrapper } from './components/MaintenanceWrapper';
@@ -260,6 +261,20 @@ function App() {
                         </Route>
                       </Route>
 
+                      {/* Accounting section (migration 122). Parent gated by
+                          the `accounting` flag. Hosts the Tax report — which
+                          relocates here from the CRM sub-nav when accounting
+                          is on — plus the future inbound-invoice / expenses
+                          pages. Each sub-route is independently flagged. */}
+                      <Route element={<RequireFeature flag="accounting" />}>
+                        <Route path="accounting" element={<AccountingLayout />}>
+                          <Route element={<RequireFeature flag="taxReport" />}>
+                            <Route path="tax-report" element={<TaxReportPage />} />
+                          </Route>
+                          <Route index element={<Navigate to="/admin/accounting/tax-report" replace />} />
+                        </Route>
+                      </Route>
+
                       {/* Old /admin/customers paths now live under
                           /admin/clients/accounts. Kept indefinitely as
                           redirects so existing bookmarks and email links

frontend/src/components/admin/AccountingLayout.tsx

@@ -0,0 +1,141 @@
+/**
+ * Accounting section layout (migration 122).
+ *
+ * Wraps /admin/accounting/* routes with a Settings-style left sub-nav,
+ * mirroring ClientsLayout. Today it hosts the Tax report (relocated here
+ * from CRM when the `accounting` flag is on); the inbound-document inbox and
+ * expenses pages slot in as additional sub-nav entries when their UIs land.
+ */
+import React from 'react';
+import { NavLink, Outlet, useLocation, useNavigate } from 'react-router-dom';
+import { useTranslation } from 'react-i18next';
+import { Landmark, Calculator } from 'lucide-react';
+import type { LucideIcon } from 'lucide-react';
+import { useFeatureFlags, type FeatureKey } from '../../contexts/FeatureFlagsContext';
+
+interface NavItem {
+  key: string;
+  to: string;
+  label: string;
+  icon: LucideIcon;
+  /** Feature flag that must be ON for this entry to render. */
+  featureFlag: FeatureKey;
+}
+
+export const AccountingLayout: React.FC = () => {
+  const { t } = useTranslation();
+  const location = useLocation();
+  const navigate = useNavigate();
+  const { flags } = useFeatureFlags();
+
+  const navItems: NavItem[] = [
+    {
+      key: 'tax-report',
+      to: '/admin/accounting/tax-report',
+      label: t('accounting.subnav.taxReport', 'Tax'),
+      icon: Calculator,
+      featureFlag: 'taxReport',
+    },
+    // Future Accounting sub-features (inbound inbox, expenses) slot in here
+    // once their pages land, e.g.:
+    //   { key: 'inbox', to: '/admin/accounting/inbox', featureFlag: 'accounting' }
+    //   { key: 'expenses', to: '/admin/accounting/expenses', featureFlag: 'accounting' }
+  ];
+
+  const enabledItems = navItems.filter((item) => flags[item.featureFlag]);
+
+  const header = (
+    <div className="mb-6">
+      <h1 className="text-2xl font-bold text-neutral-900 dark:text-neutral-100">
+        {t('accounting.title', 'Accounting')}
+      </h1>
+      <p className="text-neutral-600 dark:text-neutral-400 mt-1">
+        {t('accounting.subtitle', 'Inbound supplier invoices, expenses and reporting.')}
+      </p>
+    </div>
+  );
+
+  if (enabledItems.length === 0) {
+    return (
+      <div>
+        {header}
+        <div className="rounded-xl border border-dashed border-neutral-300 dark:border-neutral-700 bg-neutral-50 dark:bg-neutral-900 p-8 text-center">
+          <Landmark className="w-10 h-10 mx-auto mb-3 text-neutral-400" />
+          <h2 className="text-lg font-semibold text-neutral-900 dark:text-neutral-100 mb-1">
+            {t('accounting.empty.title', 'No accounting features enabled')}
+          </h2>
+          <p className="text-sm text-neutral-600 dark:text-neutral-400">
+            {t('accounting.empty.body', 'Enable the Tax report (or another accounting sub-feature) under Settings → Features to get started.')}
+          </p>
+        </div>
+      </div>
+    );
+  }
+
+  return (
+    <div>
+      {header}
+
+      <div className="grid grid-cols-1 lg:grid-cols-[220px_1fr] gap-6 lg:gap-8">
+        {/* Mobile: native select dropdown */}
+        <div className="lg:hidden">
+          <label htmlFor="accounting-section" className="sr-only">
+            {t('accounting.navAriaLabel', 'Accounting navigation')}
+          </label>
+          <select
+            id="accounting-section"
+            value={location.pathname}
+            onChange={(e) => navigate(e.target.value)}
+            className="w-full rounded-md border border-neutral-300 dark:border-neutral-600 bg-white dark:bg-neutral-800 px-3 py-2 text-sm font-medium text-neutral-900 dark:text-neutral-100 focus:outline-none focus:ring-2 focus:ring-primary-500"
+          >
+            {enabledItems.map((item) => (
+              <option key={item.key} value={item.to}>{item.label}</option>
+            ))}
+          </select>
+        </div>
+
+        {/* Desktop: sticky left rail */}
+        <aside className="hidden lg:block">
+          <nav
+            aria-label={t('accounting.navAriaLabel', 'Accounting navigation')}
+            className="sticky top-6 space-y-1"
+          >
+            {enabledItems.map((item) => {
+              const Icon = item.icon;
+              return (
+                <NavLink
+                  key={item.key}
+                  to={item.to}
+                  className={({ isActive }) =>
+                    `group w-full flex items-center gap-2.5 px-3 py-2 rounded-md text-sm font-medium transition-colors ${
+                      isActive
+                        ? 'bg-accent-dark text-white'
+                        : 'text-neutral-700 dark:text-neutral-300 hover:bg-neutral-100 dark:hover:bg-neutral-800'
+                    }`
+                  }
+                >
+                  {({ isActive }) => (
+                    <>
+                      <Icon
+                        className={`w-4 h-4 flex-shrink-0 ${
+                          isActive
+                            ? 'text-white'
+                            : 'text-neutral-500 dark:text-neutral-400 group-hover:text-neutral-700 dark:group-hover:text-neutral-200'
+                        }`}
+                      />
+                      <span className="truncate">{item.label}</span>
+                    </>
+                  )}
+                </NavLink>
+              );
+            })}
+          </nav>
+        </aside>
+
+        <div className="min-w-0">
+          <Outlet />
+        </div>
+      </div>
+    </div>
+  );
+};

frontend/src/components/admin/AdminSidebar.tsx

@@ -10,6 +10,7 @@ import {
   X,
   Users,
   Briefcase,
+  Landmark,
   PanelLeftClose,
   PanelLeftOpen,
 } from 'lucide-react';
@@ -96,6 +97,16 @@ const navigation: NavItem[] = [
       'taxReport', 'hoursLogging', 'contracts', 'calendar',
     ],
   },
+  // Accounting section (migration 122) — inbound supplier invoices,
+  // expenses + re-bill, and the tax report (which relocates here from
+  // the CRM sub-nav when `accounting` is on). Gated by the `accounting`
+  // master flag; the sub-pages inside AccountingLayout are each
+  // independently feature-gated.
+  {
+    nameKey: 'navigation.accounting', href: '/admin/accounting', icon: Landmark,
+    permission: 'accounting.view',
+    featureFlag: 'accounting',
+  },
 ];
 
 export const AdminSidebar: React.FC<AdminSidebarProps> = ({ isOpen, onClose, collapsed = false, onToggleCollapse }) => {

frontend/src/components/admin/ClientsLayout.tsx

@@ -99,7 +99,13 @@ export const ClientsLayout: React.FC = () => {
     },
   ];
 
-  const enabledItems = navItems.filter((item) => flags[item.featureFlag]);
+  const enabledItems = navItems.filter((item) => {
+    if (!flags[item.featureFlag]) return false;
+    // When the Accounting area is enabled, the tax report relocates out
+    // of CRM and under Accounting — hide it here so it isn't in both.
+    if (item.key === 'tax-report' && flags.accounting) return false;
+    return true;
+  });
 
   // When the parent `clients` flag is on but no sub-feature is enabled,
   // there's nothing to render. Settings → Features is one click away

frontend/src/contexts/FeatureFlagsContext.tsx

@@ -45,6 +45,10 @@ export const DEFAULT_FLAGS: FeatureFlags = {
   // Settings → Features once they've reviewed the seeded block
   // library with their lawyer.
   contracts: false,
+  // Accounting (migration 122). Top-level Accounting area (inbound
+  // supplier invoices, expenses + re-bill). When ON, the tax report
+  // moves out of the CRM sub-nav and under Accounting. Strictly opt-in.
+  accounting: false,
 };
 
 export const FEATURE_FLAGS_QUERY_KEY = ['feature-flags'] as const;

frontend/src/features/settings/tabs/FeaturesTab.tsx

@@ -16,6 +16,7 @@ import {
   Briefcase,
   Wrench,
   Calculator,
+  Landmark,
 } from 'lucide-react';
 import { useTranslation } from 'react-i18next';
 import { Button, Card } from '../../../components/common';
@@ -278,6 +279,20 @@ export const FeaturesTab: React.FC = () => {
             ) : undefined}
           />
 
+          <FeatureCard
+            icon={Landmark}
+            title={t('settings.features.accounting.title', 'Accounting')}
+            description={t(
+              'settings.features.accounting.description',
+              'Capture incoming supplier invoices (upload or phone/tablet camera), categorize expenses and re-bill costs to clients on the relevant event. When enabled, the Tax report moves out of CRM into a dedicated Accounting section. VAT / tax treatment is provided as guidance only — verify with your Treuhänder before relying on it.',
+            )}
+            status="new"
+            statusLabel={statusLabel('new')}
+            sidebarLabel={t('settings.features.accounting.sidebar', 'Accounting')}
+            enabled={staged.accounting}
+            onToggle={(next) => setFlag('accounting', next)}
+          />
+
           <FeatureCard
             icon={Briefcase}
             title={t('settings.features.hoursLogging.title', 'Hours logging')}

frontend/src/i18n/locales/de.json

@@ -196,6 +196,7 @@
     "users": "Benutzer",
     "calendar": "Kalender",
     "clients": "CRM",
+    "accounting": "Buchhaltung",
     "betaTag": "Beta"
   },
   "eventTypes": {
@@ -1635,6 +1636,11 @@
         "sidebar": "Steuer",
         "requiresBills": "Bitte zuerst Rechnungen aktivieren — die Steuerliste liest aus Ihren Rechnungen."
       },
+      "accounting": {
+        "title": "Buchhaltung",
+        "description": "Eingehende Lieferantenrechnungen erfassen (Upload oder Handy-/Tablet-Kamera), Aufwände kategorisieren und Kosten dem passenden Event des Kunden weiterverrechnen. Wenn aktiviert, wandert die Steuerliste aus dem CRM in einen eigenen Buchhaltungsbereich. MwSt-/Steuerbehandlung dient nur als Orientierung — vor dem Verlassen darauf mit Ihrem Treuhänder prüfen.",
+        "sidebar": "Buchhaltung"
+      },
       "analytics": {
         "title": "Statistiken",
         "description": "Speichernutzung, Galerie-Aufrufe, Download-Zahlen und Statistiken pro Veranstaltung."
@@ -3375,6 +3381,18 @@
       "development": "Entwicklung"
     }
   },
+  "accounting": {
+    "title": "Buchhaltung",
+    "subtitle": "Eingehende Lieferantenrechnungen, Aufwände und Auswertungen.",
+    "navAriaLabel": "Buchhaltungs-Navigation",
+    "empty": {
+      "title": "Keine Buchhaltungsfunktionen aktiviert",
+      "body": "Aktiviere die Steuerliste (oder eine andere Buchhaltungs-Unterfunktion) unter Einstellungen → Funktionen, um loszulegen."
+    },
+    "subnav": {
+      "taxReport": "Steuer"
+    }
+  },
   "calendar": {
     "pageTitle": "Kalender",
     "subtitle": "Termine, erfasste Stunden und offene Angebote/Verträge in einer Ansicht.",

frontend/src/i18n/locales/en.json

@@ -196,6 +196,7 @@
     "users": "Users",
     "calendar": "Calendar",
     "clients": "CRM",
+    "accounting": "Accounting",
     "betaTag": "Beta"
   },
   "archives": {
@@ -1193,6 +1194,11 @@
         "sidebar": "Tax",
         "requiresBills": "Enable Bills first — the tax report reads from your invoices."
       },
+      "accounting": {
+        "title": "Accounting",
+        "description": "Capture incoming supplier invoices (upload or phone/tablet camera), categorize expenses and re-bill costs to clients on the relevant event. When enabled, the Tax report moves out of CRM into a dedicated Accounting section. VAT / tax treatment is provided as guidance only — verify with your Treuhänder before relying on it.",
+        "sidebar": "Accounting"
+      },
       "analytics": {
         "title": "Analytics",
         "description": "Storage usage, gallery views, download counts, and per-event stats."
@@ -3375,6 +3381,18 @@
       "development": "Development"
     }
   },
+  "accounting": {
+    "title": "Accounting",
+    "subtitle": "Inbound supplier invoices, expenses and reporting.",
+    "navAriaLabel": "Accounting navigation",
+    "empty": {
+      "title": "No accounting features enabled",
+      "body": "Enable the Tax report (or another accounting sub-feature) under Settings → Features to get started."
+    },
+    "subnav": {
+      "taxReport": "Tax"
+    }
+  },
   "calendar": {
     "pageTitle": "Calendar",
     "subtitle": "Events, logged hours, and pending quotes/contracts in one view.",

frontend/src/services/featureFlags.service.ts

@@ -41,7 +41,12 @@ export type FeatureKey =
   // upload. Independent of quotes / bills — contracts can be sent on
   // their own. Seeded block bodies are examples only; admins must
   // have their lawyer review before sending. See docs/crm-disclaimers.md.
-  | 'contracts';
+  | 'contracts'
+  // Accounting (migration 122). Top-level Accounting area — inbound
+  // supplier invoices, expenses + re-bill, plus the tax report, which
+  // relocates here from the CRM sub-nav when this flag is on. Strictly
+  // opt-in; independent of the CRM flags.
+  | 'accounting';
 
 export type FeatureFlags = Record<FeatureKey, boolean>;