feat: implement onboarding flow with complex creation and email verification, and add Zustand for state management

AGENTS.md

@@ -149,3 +149,47 @@ The app supports users with multiple complexes. Each user has a role per complex
 ### Profile Role
 
 The profile page shows the user's role for the **selected complex**, not the global user role. This is fetched from `ComplexUser` table using the cookie value.
+
+## Frontend API Client
+
+The API client is split into modular files for better maintainability and testability.
+
+### Structure
+
+```
+lib/
+├── api-client.ts    # Main barrel file (~70 lines)
+└── api/
+    ├── base.ts        # ApiClientError, configureApiClient, apiBaseUrl
+    ├── http.ts        # Axios instance with interceptors
+    ├── index.ts       # Re-exports all resources
+    └── resources/
+        ├── complexes.ts   # Complex endpoints
+        ├── courts.ts      # Court endpoints
+        ├── bookings.ts    # Public & admin booking endpoints
+        ├── user.ts        # User profile endpoint
+        ├── sports.ts      # Sport endpoints
+        ├── onboarding.ts  # Onboarding endpoints
+        └── plans.ts       # Plan endpoints
+```
+
+### Using the API Client
+
+```typescript
+import { apiClient, authClient, ApiClientError, configureApiClient } from '@/lib/api-client';
+
+// Via apiClient (barrel)
+await apiClient.complexes.listMine();
+await apiClient.publicBookings.getAvailability('my-club', { date: '2026-04-20' });
+
+// Direct imports (for better tree-shaking)
+import { complexes, getAvailability } from '@/lib/api';
+await complexes.listMine();
+await getAvailability('my-club', { date: '2026-04-20' });
+```
+
+### Adding a New Resource
+
+1. Create `lib/api/resources/[resource].ts`
+2. Export functions using `http` from `../http`
+3. Add exports in `lib/api/index.ts`