feat: implement frontend with TDD (Part 8)

- Scaffold Vite + React 19 + TypeScript strict project
- Neumorphic dark design system (Tailwind v3, amber/orange LED accents)
- Zustand stores for auth (persist) and UI state (notifications, sidebar)
- TanStack Query v5 hooks for server CRUD operations
- WebSocket hook with reconnection backoff and query invalidation
- Components: StatusLed, Sidebar, ServerCard, LoginPage, DashboardPage
- Protected routing with auth guard
- Axios client with JWT interceptor and 401 redirect
- 68 tests across 11 test files (89% statement coverage, 90% function coverage)
- TDD workflow: RED validated, GREEN achieved, coverage verified

frontend/src/lib/api.ts

@@ -0,0 +1,34 @@
+import axios from "axios";
+
+const API_BASE = import.meta.env.VITE_API_URL ?? "http://localhost:8000";
+
+export const apiClient = axios.create({
+  baseURL: API_BASE,
+  headers: { "Content-Type": "application/json" },
+  timeout: 30_000,
+});
+
+apiClient.interceptors.request.use((config) => {
+  const token = localStorage.getItem("languard_token");
+  if (token) {
+    config.headers.Authorization = `Bearer ${token}`;
+  }
+  return config;
+});
+
+apiClient.interceptors.response.use(
+  (response) => response,
+  (error) => {
+    if (error.response?.status === 401) {
+      localStorage.removeItem("languard_token");
+      window.location.href = "/login";
+    }
+    return Promise.reject(error);
+  },
+);
+
+export type ApiResponse<T> = {
+  success: boolean;
+  data: T;
+  error?: string;
+};