feat: initial workflow portal - multi-tenant architecture

- Backend: Node.js + Express + TypeScript + Prisma + PostgreSQL
- Frontend: React + TypeScript + Tailwind CSS + Vite
- Multi-tenant with role-based access (SystemAdmin, Technician, Customer)
- Workflow editor with drag-and-drop steps
- JWT authentication with refresh tokens
- German UI throughout

.gitignore

@@ -0,0 +1,10 @@
+node_modules/
+dist/
+build/
+.env
+*.log
+.DS_Store
+coverage/
+.nyc_output/
+*.pem
+*.key