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/config/src/constants.ts

@@ -0,0 +1,26 @@
+/**
+ * Shared application constants
+ */
+
+/** Milliseconds before token expiry at which a proactive refresh is triggered */
+export const TOKEN_REFRESH_THRESHOLD_MS = 5 * 60 * 1_000; // 5 minutes
+
+/** Default access token lifetime (matches backend default: 15 min) */
+export const ACCESS_TOKEN_LIFETIME_MS = 15 * 60 * 1_000;
+
+/** Default refresh token lifetime (matches backend default: 7 days) */
+export const REFRESH_TOKEN_LIFETIME_MS = 7 * 24 * 60 * 60 * 1_000;
+
+/** Path to the CLI config file */
+export const CLI_CONFIG_PATH = '~/.effigenix/config.json';
+
+/** File permission octal for the CLI config file (owner read/write only) */
+export const CLI_CONFIG_FILE_MODE = 0o600;
+
+/** Pagination defaults */
+export const DEFAULT_PAGE_SIZE = 20;
+export const MAX_PAGE_SIZE = 100;
+
+/** Password constraints (must match backend validation) */
+export const PASSWORD_MIN_LENGTH = 8;
+export const PASSWORD_MAX_LENGTH = 128;