feat: Implement API modules for admin, auth, exam, result, and setup functionalities

- Created adminApi.ts for admin-related operations including user management and site settings.
- Developed authApi.ts for authentication processes such as registration, login, and profile management.
- Added examApi.ts for handling exam CRUD operations.
- Introduced resultApi.ts for managing results submission and retrieval.
- Established setupApi.ts for initial setup processes and status checks.
- Created ErrorBoundary component to handle rendering errors gracefully in the frontend.
- Re-exported shared API utilities in index.ts for easier access.

frontend/src/api/setupApi.ts

@@ -0,0 +1,38 @@
+import { apiFetch } from '../utils/api.js'
+
+export interface SetupStatus {
+  completed: boolean
+  siteTitle?: string
+}
+
+export function getSetupStatus(): Promise<SetupStatus> {
+  return apiFetch('/api/setup/status')
+}
+
+export interface SetupPayload {
+  email: string
+  password: string
+  displayName: string
+  smtpHost?: string
+  smtpPort?: string
+  smtpUser?: string
+  smtpPass?: string
+  smtpFrom?: string
+  smtpSecure?: string
+  appUrl?: string
+}
+
+export interface SetupResponse {
+  message: string
+  token: string
+  user: {
+    id: number
+    email: string
+    displayName: string
+    role: 'user' | 'admin'
+  }
+}
+
+export function completeSetup(data: SetupPayload): Promise<SetupResponse> {
+  return apiFetch('/api/setup', { method: 'POST', body: JSON.stringify(data) })
+}