Add LoadingSpinner and API client with auth interceptors

src/api/client.ts

@@ -0,0 +1,23 @@
+import axios from 'axios';
+
+export const apiClient = axios.create({
+  baseURL: import.meta.env.VITE_API_BASE_URL ?? '/api',
+  headers: { 'Content-Type': 'application/json' },
+});
+
+apiClient.interceptors.request.use((config) => {
+  const token = localStorage.getItem('access_token');
+  if (token) config.headers.Authorization = `Bearer ${token}`;
+  return config;
+});
+
+apiClient.interceptors.response.use(
+  (r) => r,
+  (err) => {
+    if (err.response?.status === 401) {
+      localStorage.removeItem('access_token');
+      window.location.href = '/login';
+    }
+    return Promise.reject(err);
+  },
+);

src/components/LoadingSpinner.tsx

@@ -0,0 +1,14 @@
+import React from 'react';
+
+interface Props { size?: number; }
+
+export const LoadingSpinner: React.FC<Props> = ({ size = 32 }) => (
+  <div role="status" aria-label="Loading" style={{ width: size, height: size }}>
+    <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth={2}>
+      <circle cx={12} cy={12} r={10} strokeOpacity={0.25} />
+      <path d="M12 2 a10 10 0 0 1 10 10" strokeLinecap="round">
+        <animateTransform attributeName="transform" type="rotate" from="0 12 12" to="360 12 12" dur="0.8s" repeatCount="indefinite" />
+      </path>
+    </svg>
+  </div>
+);