feat(frontend): TypeScript-Monorepo mit Terminal-UI für Effigenix ERP

Monorepo-Setup (pnpm workspaces) mit vier shared Packages und einer TUI-App:

Shared Packages:
- @effigenix/types: TypeScript-DTOs (UserDTO, RoleDTO, AuthDTO, Enums)
- @effigenix/config: API-Konfiguration und Shared Constants
- @effigenix/validation: Zod-Schemas für Username, E-Mail und Passwort
- @effigenix/api-client: axios-Client mit JWT-Handling (proaktiver + reaktiver
  Token-Refresh), AuthInterceptor, ErrorInterceptor, Resources für auth/users/roles

TUI (apps/cli, Ink 5 / React):
- Authentication: Login/Logout, Session-Restore beim Start, JWT-Refresh
- User Management: Liste, Anlage (Zod-Inline-Validation), Detailansicht,
  Passwort ändern, Sperren/Entsperren mit ConfirmDialog
- Role Management: Liste, Detailansicht, Zuweisen/Entfernen per RoleSelectList (↑↓)
- UX: SuccessDisplay (Auto-Dismiss 3 s), ConfirmDialog (J/N),
  FormInput mit Inline-Fehlern, StatusBar mit API-URL
- Layout: Fullscreen-Modus (alternate screen buffer), Header mit eingeloggtem User
- Tests: vitest + ink-testing-library (15 Tests)

frontend/packages/api-client/src/client.ts

@@ -0,0 +1,40 @@
+/**
+ * Base axios client for the Effigenix API
+ */
+
+import axios, { type AxiosInstance } from 'axios';
+import { type ApiConfig, DEFAULT_API_CONFIG } from '@effigenix/config';
+import { setupAuthInterceptor } from './interceptors/auth-interceptor.js';
+import { setupRefreshInterceptor } from './interceptors/refresh-interceptor.js';
+import { setupErrorInterceptor } from './interceptors/error-interceptor.js';
+import type { TokenProvider } from './token-provider.js';
+
+export type { AxiosInstance };
+
+/**
+ * Creates and configures an axios instance with all interceptors.
+ *
+ * @param config - Optional API configuration (defaults to localhost:8080)
+ * @param tokenProvider - Provides access/refresh tokens and handles token storage
+ */
+export function createApiClient(
+  config: Partial<ApiConfig> = {},
+  tokenProvider: TokenProvider,
+): AxiosInstance {
+  const resolvedConfig: ApiConfig = { ...DEFAULT_API_CONFIG, ...config };
+
+  const client = axios.create({
+    baseURL: resolvedConfig.baseUrl,
+    timeout: resolvedConfig.timeoutMs,
+    headers: {
+      'Content-Type': 'application/json',
+      Accept: 'application/json',
+    },
+  });
+
+  setupAuthInterceptor(client, tokenProvider);
+  setupRefreshInterceptor(client, tokenProvider);
+  setupErrorInterceptor(client);
+
+  return client;
+}