feat: Mobile chart optimization + VIP customer settings

## Task 4: Mobile Chart Optimization ✅

**Problem:** Too many data points = tight/crowded lines on mobile

**Solution:** Horizontal scroll container

**Implementation:**
- ChartCard component enhanced with mobile scroll
- Calculates minimum width based on data points (40px per point)
- Desktop: Full width responsive
- Mobile: Fixed width chart in scrollable container

```tsx
// ChartCard.tsx
const mobileMinWidth = Math.max(600, dataPoints * 40);

<div className="overflow-x-auto -mx-6 px-6 md:mx-0 md:px-0">
  <div style={{ minWidth: `${mobileMinWidth}px` }}>
    {children}
  </div>
</div>
```

**Benefits:**
- ✅ All data visible (no loss)
- ✅ Natural swipe gesture
- ✅ Readable spacing
- ✅ Works for all chart types
- ✅ No data aggregation needed

---

## Task 5: VIP Customer Settings ✅

**New Feature:** Configure VIP customer qualification criteria

### Backend (PHP)

**Files Created:**
- `includes/Compat/CustomerSettingsProvider.php`
  - VIP settings management
  - VIP detection logic
  - Customer stats calculation

**API Endpoints:**
- `GET /store/customer-settings` - Fetch settings
- `POST /store/customer-settings` - Save settings

**Settings:**
```php
woonoow_vip_min_spent = 1000
woonoow_vip_min_orders = 10
woonoow_vip_timeframe = 'all' | '30' | '90' | '365'
woonoow_vip_require_both = true
woonoow_vip_exclude_refunded = true
```

**VIP Detection:**
```php
CustomerSettingsProvider::is_vip_customer($customer_id)
CustomerSettingsProvider::get_vip_stats($customer_id)
```

### Frontend (React)

**Files Created:**
- `admin-spa/src/routes/Settings/Customers.tsx`

**Features:**
- 💰 Minimum total spent (currency input)
- �� Minimum order count (number input)
- 📅 Timeframe selector (all-time, 30/90/365 days)
- ⚙️ Require both criteria toggle
- 🚫 Exclude refunded orders toggle
- 👑 Live preview of VIP qualification

**Navigation:**
- Added to Settings menu
- Route: `/settings/customers`
- Position: After Tax, before Notifications

---

## Summary

✅ **Mobile Charts:** Horizontal scroll for readable spacing
✅ **VIP Settings:** Complete backend + frontend implementation

**Mobile Chart Strategy:**
- Minimum 600px width
- 40px per data point
- Smooth horizontal scroll
- Desktop remains responsive

**VIP Customer System:**
- Flexible qualification criteria
- Multiple timeframes
- AND/OR logic support
- Refunded order exclusion
- Ready for customer list integration

**All tasks complete!** 🎉

includes/Api/StoreController.php

@@ -10,6 +10,7 @@
 namespace WooNooW\API;
 
 use WooNooW\Compat\StoreSettingsProvider;
+use WooNooW\Compat\CustomerSettingsProvider;
 use WP_REST_Controller;
 use WP_REST_Server;
 use WP_REST_Request;
@@ -85,6 +86,24 @@ class StoreController extends WP_REST_Controller {
                 'permission_callback' => [$this, 'check_permission'],
             ],
         ]);
+        
+        // GET /woonoow/v1/store/customer-settings
+        register_rest_route($this->namespace, '/' . $this->rest_base . '/customer-settings', [
+            [
+                'methods' => WP_REST_Server::READABLE,
+                'callback' => [$this, 'get_customer_settings'],
+                'permission_callback' => [$this, 'check_permission'],
+            ],
+        ]);
+        
+        // POST /woonoow/v1/store/customer-settings
+        register_rest_route($this->namespace, '/' . $this->rest_base . '/customer-settings', [
+            [
+                'methods' => WP_REST_Server::EDITABLE,
+                'callback' => [$this, 'save_customer_settings'],
+                'permission_callback' => [$this, 'check_permission'],
+            ],
+        ]);
     }
     
     /**
@@ -241,6 +260,75 @@ class StoreController extends WP_REST_Controller {
         }
     }
     
+    /**
+     * Get customer settings
+     * 
+     * @param WP_REST_Request $request Request object
+     * @return WP_REST_Response|WP_Error Response object or error
+     */
+    public function get_customer_settings(WP_REST_Request $request) {
+        try {
+            $settings = CustomerSettingsProvider::get_settings();
+            
+            $response = rest_ensure_response($settings);
+            $response->header('Cache-Control', 'max-age=60');
+            
+            return $response;
+        } catch (\Exception $e) {
+            return new WP_Error(
+                'get_customer_settings_failed',
+                $e->getMessage(),
+                ['status' => 500]
+            );
+        }
+    }
+    
+    /**
+     * Save customer settings
+     * 
+     * @param WP_REST_Request $request Request object
+     * @return WP_REST_Response|WP_Error Response object or error
+     */
+    public function save_customer_settings(WP_REST_Request $request) {
+        try {
+            $settings = $request->get_json_params();
+            
+            if (empty($settings)) {
+                return new WP_Error(
+                    'invalid_settings',
+                    __('Invalid settings data', 'woonoow'),
+                    ['status' => 400]
+                );
+            }
+            
+            $updated = CustomerSettingsProvider::update_settings($settings);
+            
+            if (!$updated) {
+                return new WP_Error(
+                    'update_failed',
+                    __('Failed to update customer settings', 'woonoow'),
+                    ['status' => 500]
+                );
+            }
+            
+            // Return updated settings
+            $new_settings = CustomerSettingsProvider::get_settings();
+            
+            return new WP_REST_Response([
+                'success' => true,
+                'message' => __('Customer settings updated successfully', 'woonoow'),
+                'settings' => $new_settings,
+            ], 200);
+            
+        } catch (\Exception $e) {
+            return new WP_Error(
+                'save_customer_settings_failed',
+                $e->getMessage(),
+                ['status' => 500]
+            );
+        }
+    }
+    
     /**
      * Check permission
      *