feat(T01): auth + user management + RBAC + base frontend + i18n

- Backend: FastAPI, JWT auth (HS256), bcrypt, RBAC middleware
- User CRUD (admin-only), soft-delete, pagination
- Pydantic BaseSettings config, async SQLAlchemy 2.0
- 50 backend tests, 88% coverage
- Frontend: Next.js 14 App Router, Tailwind, design tokens
- Login page, auth context, API client with auto-refresh
- i18n: next-intl, DE/EN (31 keys each)
- 6 base UI components (Button, Input, Card, Table, Modal, Toast)
- 12 frontend tests, npm build success

frontend/app/globals.css

@@ -0,0 +1,22 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+:root {
+  --color-primary: #2563eb;
+  --color-primary-hover: #1d4ed8;
+  --color-secondary: #64748b;
+  --color-background: #f8fafc;
+  --color-surface: #ffffff;
+  --color-text: #1e293b;
+  --color-text-muted: #64748b;
+  --color-error: #dc2626;
+  --color-success: #16a34a;
+  --color-border: #e2e8f0;
+}
+
+body {
+  background-color: var(--color-background);
+  color: var(--color-text);
+  font-family: system-ui, -apple-system, sans-serif;
+}