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/index.ts

@@ -0,0 +1,69 @@
+/**
+ * @effigenix/api-client
+ *
+ * Type-safe HTTP client for the Effigenix ERP API.
+ *
+ * Usage:
+ *
+ * ```ts
+ * import { createEffigenixClient } from '@effigenix/api-client';
+ *
+ * const client = createEffigenixClient(tokenProvider);
+ * const users = await client.users.list();
+ * ```
+ */
+
+export { createApiClient } from './client.js';
+export type { TokenProvider } from './token-provider.js';
+export { createAuthResource } from './resources/auth.js';
+export { createUsersResource } from './resources/users.js';
+export { createRolesResource } from './resources/roles.js';
+export {
+  ApiError,
+  AuthenticationError,
+  NetworkError,
+  RefreshTokenExpiredError,
+} from './errors.js';
+export type { ValidationErrorDetail } from './errors.js';
+export type {
+  LoginRequest,
+  LoginResponse,
+  RefreshTokenRequest,
+  AuthResource,
+} from './resources/auth.js';
+export type {
+  UserDTO,
+  RoleDTO,
+  CreateUserRequest,
+  UpdateUserRequest,
+  ChangePasswordRequest,
+  AssignRoleRequest,
+  UsersResource,
+} from './resources/users.js';
+export type { RolesResource } from './resources/roles.js';
+
+import { createApiClient } from './client.js';
+import { createAuthResource } from './resources/auth.js';
+import { createUsersResource } from './resources/users.js';
+import { createRolesResource } from './resources/roles.js';
+import type { TokenProvider } from './token-provider.js';
+import type { ApiConfig } from '@effigenix/config';
+
+/**
+ * Convenience factory that creates a fully-configured Effigenix API client
+ * with all resource modules attached.
+ */
+export function createEffigenixClient(
+  tokenProvider: TokenProvider,
+  config: Partial<ApiConfig> = {},
+) {
+  const axiosClient = createApiClient(config, tokenProvider);
+
+  return {
+    auth: createAuthResource(axiosClient),
+    users: createUsersResource(axiosClient),
+    roles: createRolesResource(axiosClient),
+  };
+}
+
+export type EffigenixClient = ReturnType<typeof createEffigenixClient>;