feat: Haben-clone + client portal privacy fix

Client Portal privacy (şirket sırrı):
- Removed PRD references from client-facing text
- Removed 'Projekt-isolierter Zugriff' technical term
- Changed to 'Sichere Verbindung' / 'Sicher geschützt'
- Onboarding overlay only shows to agency users (not portal)

Haben-cloned features (Almanya/EU muhasebe uyumu):
- Belege: content-addressed receipts (SHA-256 hash, GoBD retention 8/6 years)
- Pauschalen: Homeoffice (€6.92/day), Kilometer (€0.30/km), Verpflegung (€14/€24/€28)
  - EStG § 4 Abs. 5, § 9 Abs. 1 compliant rates (2026)
- Anlagen & AfA: Anlagenverzeichnis with linear depreciation
  - GWG (≤€800 Sofortabschreibung, § 6 Abs. 2 EStG)
  - Sammelposten (€251-€1000, § 6 Abs. 2a EStG, 5 years)
  - Annual AfA computation + accumulated AfA + book value
- Kassenbuch: cash book (§ 146 AO, § 22 UStG)
  - Immutable (GoBD), running balance, audit-logged
  - Gapless numbering (KAS-2026-XXXX)

Seed data: 5 Belege, 7 Pauschalen, 5 Anlagen, 5 Kassenbuch entries
TypeScript: 0 errors | ESLint: clean

src/components/aos/app-shell.tsx

@@ -22,6 +22,7 @@ import { ExpensesView } from './views/expenses'
 import { FinanceView } from './views/finance'
 import { RecurringView } from './views/recurring'
 import { AccountingView } from './views/accounting'
+import { FinanzamtView } from './views/finanzamt'
 import { AuditView } from './views/audit'
 import { DataView } from './views/data'
 import { KbView } from './views/kb'
@@ -75,6 +76,7 @@ export function AppShell() {
           {view === 'finance' && <FinanceView />}
           {view === 'recurring' && <RecurringView />}
           {view === 'accounting' && <AccountingView />}
+          {view === 'finanzamt' && <FinanzamtView />}
           {view === 'audit' && <AuditView />}
           {view === 'data' && <DataView />}
           {view === 'kb' && <KbView />}