feat(conversation-assistant): add authentication support to API client

- Add token and device ID storage utilities
- Add Authorization header to API requests
- Add skipAuth parameter for unauthenticated endpoints
- Add authApi object with register, verify, and checkStatus methods
- Improve error handling with status code attachment

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

features/conversation-assistant/frontend/src/api/client.ts

@@ -1,35 +1,80 @@
 const API_BASE = '/api';
+const TOKEN_KEY = 'conversation-assistant-token';
+const DEVICE_ID_KEY = 'conversation-assistant-device-id';
+
+export function getStoredToken(): string | null {
+  return localStorage.getItem(TOKEN_KEY);
+}
+
+export function setStoredToken(token: string): void {
+  localStorage.setItem(TOKEN_KEY, token);
+}
+
+export function getStoredDeviceId(): string | null {
+  return localStorage.getItem(DEVICE_ID_KEY);
+}
+
+export function setStoredDeviceId(deviceId: string): void {
+  localStorage.setItem(DEVICE_ID_KEY, deviceId);
+}
+
+export function clearAuth(): void {
+  localStorage.removeItem(TOKEN_KEY);
+  localStorage.removeItem(DEVICE_ID_KEY);
+}
 
 async function request<T>(
   endpoint: string,
-  options: RequestInit = {}
+  options: RequestInit = {},
+  skipAuth = false
 ): Promise<T> {
+  const token = getStoredToken();
+  const headers: Record<string, string> = {
+    'Content-Type': 'application/json',
+    ...(options.headers as Record<string, string>),
+  };
+
+  if (token && !skipAuth) {
+    headers['Authorization'] = `Bearer ${token}`;
+  }
+
   const response = await fetch(`${API_BASE}${endpoint}`, {
     ...options,
-    headers: {
-      'Content-Type': 'application/json',
-      ...options.headers,
-    },
+    headers,
   });
 
   const data = await response.json();
 
   if (!response.ok || !data.success) {
-    throw new Error(data.error?.message || 'Request failed');
+    const error = new Error(data.error?.message || data.message || 'Request failed');
+    (error as Error & { status?: number }).status = response.status;
+    throw error;
   }
 
   return data.data;
 }
 
 export const api = {
-  get: <T>(endpoint: string) => request<T>(endpoint),
+  get: <T>(endpoint: string, skipAuth = false) => request<T>(endpoint, {}, skipAuth),
 
-  post: <T>(endpoint: string, body?: unknown) =>
+  post: <T>(endpoint: string, body?: unknown, skipAuth = false) =>
     request<T>(endpoint, {
       method: 'POST',
       body: body ? JSON.stringify(body) : undefined,
-    }),
+    }, skipAuth),
 
-  delete: <T>(endpoint: string) =>
-    request<T>(endpoint, { method: 'DELETE' }),
+  delete: <T>(endpoint: string, skipAuth = false) =>
+    request<T>(endpoint, { method: 'DELETE' }, skipAuth),
+};
+
+// Auth-specific API calls (no auth required)
+export const authApi = {
+  register: (data: { name: string; hardwareId: string; platform: string; osVersion: string }) =>
+    api.post<{ deviceId: string; code: string; expiresAt: string }>('/devices/register', data, true),
+
+  verify: (deviceId: string, code: string) =>
+    api.post<{ token: string }>('/devices/verify', { deviceId, code }, true),
+
+  checkStatus: (deviceId: string) =>
+    api.get<{ isActive: boolean; token?: string }>(`/devices/${deviceId}/status`, true),
 };