feat: Initial implementation of Annas Rechnungsmanager

Full-stack German accounting & invoice management web application:

- Multi-company management (Mandantenverwaltung) with full CRUD
- Invoice creation with dynamic line items and automatic tax calculation
- Sequential invoice numbering per company (RE-2024-001 format)
- §14 UStG compliant PDF invoice generation via @react-pdf/renderer
- Customer management (Kundenverwaltung) per company
- Tax reports: quarterly USt-Voranmeldung and monthly revenue overview
- Email/password authentication via NextAuth.js v5
- Responsive, modern UI with Tailwind CSS and custom shadcn/ui components
- Prisma v5 ORM with MySQL/MariaDB schema + demo seed data

Stack: Next.js 14 (App Router) · TypeScript · Prisma/MySQL · NextAuth.js

https://claude.ai/code/session_01FN53KKxo5ebrGwqFhxzkT9

tsconfig.json

@@ -0,0 +1,34 @@
+{
+  "compilerOptions": {
+    "target": "ES2017",
+    "lib": ["dom", "dom.iterable", "esnext"],
+    "allowJs": true,
+    "skipLibCheck": true,
+    "strict": true,
+    "noEmit": true,
+    "esModuleInterop": true,
+    "module": "esnext",
+    "moduleResolution": "bundler",
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "jsx": "react-jsx",
+    "incremental": true,
+    "plugins": [
+      {
+        "name": "next"
+      }
+    ],
+    "paths": {
+      "@/*": ["./src/*"]
+    }
+  },
+  "include": [
+    "next-env.d.ts",
+    "**/*.ts",
+    "**/*.tsx",
+    ".next/types/**/*.ts",
+    ".next/dev/types/**/*.ts",
+    "**/*.mts"
+  ],
+  "exclude": ["node_modules"]
+}