feat: Implement notification system with 3 subpages (Events, Channels, Templates)

## ✅ Correct Implementation Following NOTIFICATION_STRATEGY.md

### Frontend (React) - 3 Subpages

**1. Main Notifications Page** (`Notifications.tsx`)
- Tab navigation for 3 sections
- Events | Channels | Templates

**2. Events Subpage** (`Notifications/Events.tsx`)
- Configure which channels per event
- Grouped by category (Orders, Products, Customers)
- Toggle channels (Email, WhatsApp, Telegram, etc.)
- Show recipient (Admin/Customer/Both)
- Switch UI for enable/disable per channel

**3. Channels Subpage** (`Notifications/Channels.tsx`)
- List available channels
- Built-in channels (Email)
- Addon channels (WhatsApp, Telegram, SMS, Push)
- Channel status (Active/Inactive)
- Configure button for each channel
- Addon discovery cards

**4. Templates Subpage** (`Notifications/Templates.tsx`)
- Email templates (link to WooCommerce)
- Addon channel templates
- Template variables reference
- Preview and edit buttons
- Variable documentation ({order_number}, {customer_name}, etc.)

### Backend (PHP) - Bridge to WooCommerce

**NotificationsController** (`includes/Api/NotificationsController.php`)
- Bridges to WooCommerce email system
- Does NOT reinvent notification system
- Provides addon integration hooks

**REST API Endpoints:**
```
GET  /notifications/channels  - List channels (email + addons)
GET  /notifications/events     - List events (maps to WC emails)
POST /notifications/events/update - Update event channel settings
```

**Key Features:**
✅ Leverages WooCommerce emails (not reinventing)
✅ Stores settings in wp_options
✅ Provides hooks for addons:
   - `woonoow_notification_channels` filter
   - `woonoow_notification_events` filter
   - `woonoow_notification_event_updated` action

### Addon Integration

**Example: WhatsApp Addon**
```php
// Register channel
add_filter("woonoow_notification_channels", function($channels) {
    $channels[] = [
        "id" => "whatsapp",
        "label" => "WhatsApp",
        "icon" => "message-circle",
        "enabled" => true,
        "addon" => "woonoow-whatsapp",
    ];
    return $channels;
});

// React to event updates
add_action("woonoow_notification_event_updated", function($event_id, $channel_id, $enabled, $recipient) {
    if ($channel_id === "whatsapp" && $enabled) {
        // Setup WhatsApp notification for this event
    }
}, 10, 4);

// Hook into WooCommerce email triggers
add_action("woocommerce_order_status_processing", function($order_id) {
    // Send WhatsApp notification
}, 10, 1);
```

### Architecture

**NOT a new notification system** ✅
- Uses WooCommerce email infrastructure
- Maps events to WC email IDs
- Addons hook into WC triggers

**IS an extensible framework** ✅
- Unified UI for all channels
- Per-event channel configuration
- Template management
- Addon discovery

### Files Created
- `Notifications.tsx` - Main page with tabs
- `Notifications/Events.tsx` - Events configuration
- `Notifications/Channels.tsx` - Channel management
- `Notifications/Templates.tsx` - Template editor
- `NotificationsController.php` - REST API bridge

### Files Modified
- `Routes.php` - Register NotificationsController

---

**Ready for addon development!** 🚀
Next: Build Telegram addon as proof of concept

includes/Core/Bootstrap.php

@@ -19,7 +19,6 @@ use WooNooW\Core\Mail\MailQueue;
 use WooNooW\Core\Mail\WooEmailOverride;
 use WooNooW\Core\DataStores\OrderStore;
 use WooNooW\Core\MediaUpload;
-use WooNooW\Core\Notifications\NotificationManager;
 use WooNooW\Branding;
 
 class Bootstrap {
@@ -31,7 +30,6 @@ class Bootstrap {
         StandaloneAdmin::init();
         Branding::init();
         MediaUpload::init();
-        NotificationManager::init();
         
         // Addon system (order matters: Registry → Routes → Navigation)
         AddonRegistry::init();