feat: Add email and push channel enable/disable toggles

## ✅ Channel Toggle System Complete

### Backend (PHP)

**NotificationsController Updates:**
- `get_channels()` - Now reads enabled state from options
  - `woonoow_email_notifications_enabled` (default: true)
  - `woonoow_push_notifications_enabled` (default: true)
- `POST /notifications/channels/toggle` - New endpoint
- `toggle_channel()` - Callback to enable/disable channels

**Features:**
- Email notifications can be disabled
- Push notifications can be disabled
- Settings persist in wp_options
- Returns current state in channels API

### Frontend (React)

**Channels Page:**
- Added enable/disable toggle for all channels
- Switch shows "Enabled" or "Disabled" label
- Mutation with optimistic updates
- Toast notifications
- Disabled state during save
- Mobile-responsive layout

**UI Flow:**
1. User toggles channel switch
2. API call to update setting
3. Channels list refreshes
4. Toast confirmation
5. Active badge updates color

### Use Cases

**Email Channel:**
- Toggle to disable all WooCommerce email notifications
- Useful for testing or maintenance
- Can still configure SMTP settings when disabled

**Push Channel:**
- Toggle to disable all push notifications
- Subscription management still available
- Settings preserved when disabled

### Integration

✅ **Backend Storage** - wp_options
✅ **REST API** - POST endpoint
✅ **Frontend Toggle** - Switch component
✅ **State Management** - React Query
✅ **Visual Feedback** - Toast + badge colors
✅ **Mobile Responsive** - Proper layout

---

**Notification system is now complete!** 🎉

includes/Api/NotificationsController.php

@@ -138,6 +138,15 @@ class NotificationsController {
 				'permission_callback' => [$this, 'check_permission'],
 			],
 		]);
+		
+		// POST /woonoow/v1/notifications/channels/toggle
+		register_rest_route($this->namespace, '/' . $this->rest_base . '/channels/toggle', [
+			[
+				'methods' => 'POST',
+				'callback' => [$this, 'toggle_channel'],
+				'permission_callback' => [$this, 'check_permission'],
+			],
+		]);
 	}
 	
 	/**
@@ -147,19 +156,23 @@ class NotificationsController {
 	 * @return WP_REST_Response
 	 */
 	public function get_channels(WP_REST_Request $request) {
+		// Get channel enabled states
+		$email_enabled = get_option('woonoow_email_notifications_enabled', true);
+		$push_enabled = get_option('woonoow_push_notifications_enabled', true);
+		
 		$channels = [
 			[
 				'id' => 'email',
 				'label' => __('Email', 'woonoow'),
 				'icon' => 'mail',
-				'enabled' => true,
+				'enabled' => (bool) $email_enabled,
 				'builtin' => true,
 			],
 			[
 				'id' => 'push',
 				'label' => __('Push Notifications', 'woonoow'),
 				'icon' => 'bell',
-				'enabled' => true,
+				'enabled' => (bool) $push_enabled,
 				'builtin' => true,
 			],
 		];
@@ -532,4 +545,45 @@ class NotificationsController {
 			'settings' => PushNotificationHandler::get_settings(),
 		], 200);
 	}
+	
+	/**
+	 * Toggle notification channel
+	 * 
+	 * @param WP_REST_Request $request Request object
+	 * @return WP_REST_Response
+	 */
+	public function toggle_channel(WP_REST_Request $request) {
+		$channel_id = $request->get_param('channelId');
+		$enabled = $request->get_param('enabled');
+		
+		if (empty($channel_id)) {
+			return new WP_Error(
+				'invalid_channel',
+				__('Channel ID is required', 'woonoow'),
+				['status' => 400]
+			);
+		}
+		
+		// Only allow toggling built-in channels
+		if ($channel_id === 'email') {
+			update_option('woonoow_email_notifications_enabled', (bool) $enabled);
+		} elseif ($channel_id === 'push') {
+			update_option('woonoow_push_notifications_enabled', (bool) $enabled);
+		} else {
+			return new WP_Error(
+				'invalid_channel',
+				__('Invalid channel ID', 'woonoow'),
+				['status' => 400]
+			);
+		}
+		
+		return new WP_REST_Response([
+			'success' => true,
+			'message' => sprintf(
+				__('%s notifications %s', 'woonoow'),
+				$channel_id === 'email' ? __('Email', 'woonoow') : __('Push', 'woonoow'),
+				$enabled ? __('enabled', 'woonoow') : __('disabled', 'woonoow')
+			),
+		], 200);
+	}
 }