feat: Complete Customer Notifications section

## ✅ Customer Notifications - Complete!

### Files Created

**Customer.tsx:**
- Main Customer Notifications page
- Tabs: Channels, Events, Templates
- Back button to main Notifications page

**Customer/Events.tsx:**
- Uses `/notifications/customer/events` endpoint
- Query key: `notification-customer-events`
- Shows customer-specific events (order_processing, order_completed, etc.)
- Per-channel toggles
- Recipient display

**Customer/Channels.tsx:**
- Email channel (active, built-in)
- Push notifications (requires customer opt-in)
- SMS channel (coming soon, addon)
- Customer preferences information
- Informative descriptions

### App.tsx Updates

- ✅ Added CustomerNotifications import
- ✅ Registered `/settings/notifications/customer` route

### Structure Complete

```
Settings → Notifications
├── Staff Notifications ✅
│   ├── Channels (Email, Push)
│   ├── Events (Orders, Products, Customers)
│   └── Templates
└── Customer Notifications ✅
    ├── Channels (Email, Push, SMS)
    ├── Events (Orders, Account)
    └── Templates
```

---

**Status:** Both Staff and Customer sections complete! 🎉
**Next:** Test navigation and functionality

admin-spa/src/App.tsx

@@ -202,6 +202,7 @@ import SettingsCustomers from '@/routes/Settings/Customers';
 import SettingsLocalPickup from '@/routes/Settings/LocalPickup';
 import SettingsNotifications from '@/routes/Settings/Notifications';
 import StaffNotifications from '@/routes/Settings/Notifications/Staff';
+import CustomerNotifications from '@/routes/Settings/Notifications/Customer';
 import SettingsDeveloper from '@/routes/Settings/Developer';
 import MorePage from '@/routes/More';
 
@@ -490,6 +491,7 @@ function AppRoutes() {
       <Route path="/settings/checkout" element={<SettingsIndex />} />
       <Route path="/settings/notifications" element={<SettingsNotifications />} />
       <Route path="/settings/notifications/staff" element={<StaffNotifications />} />
+      <Route path="/settings/notifications/customer" element={<CustomerNotifications />} />
       <Route path="/settings/brand" element={<SettingsIndex />} />
       <Route path="/settings/developer" element={<SettingsDeveloper />} />