feat: initial project setup

- Add .NET 8 backend with Clean Architecture
- Add React + Vite + TypeScript frontend
- Implement authentication with JWT
- Implement Azure Blob Storage client
- Implement OCR integration
- Implement supplier matching service
- Implement voucher generation
- Implement Fortnox provider
- Add unit and integration tests
- Add Docker Compose configuration

frontend/src/components/layout/Layout.tsx

@@ -0,0 +1,17 @@
+import { Outlet } from 'react-router-dom'
+import Header from './Header'
+import Sidebar from './Sidebar'
+
+export default function Layout() {
+  return (
+    <div className="min-h-screen bg-gray-50">
+      <Header />
+      <div className="flex">
+        <Sidebar />
+        <main className="flex-1 p-6">
+          <Outlet />
+        </main>
+      </div>
+    </div>
+  )
+}