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/components/ui/Input.tsx

@@ -0,0 +1,29 @@
+import { InputHTMLAttributes, forwardRef } from 'react';
+
+interface InputProps extends InputHTMLAttributes<HTMLInputElement> {
+  label?: string;
+  error?: string;
+}
+
+export const Input = forwardRef<HTMLInputElement, InputProps>(
+  ({ label, error, className = '', id, ...props }, ref) => {
+    const inputId = id || label?.toLowerCase().replace(/\s+/g, '-');
+    return (
+      <div className="w-full">
+        {label && (
+          <label htmlFor={inputId} className="block text-sm font-medium text-text mb-1">
+            {label}
+          </label>
+        )}
+        <input
+          ref={ref}
+          id={inputId}
+          className={`w-full px-3 py-2 border rounded-lg bg-surface text-text placeholder-text-muted focus:outline-none focus:ring-2 focus:ring-primary focus:border-transparent transition-colors ${error ? 'border-error' : 'border-border'} ${className}`}
+          {...props}
+        />
+        {error && <p className="mt-1 text-sm text-error">{error}</p>}
+      </div>
+    );
+  }
+);
+Input.displayName = 'Input';