Fix vendor and category page loading issues

inventory-server/src/routes/categories.js

@@ -94,17 +94,29 @@ router.get('/', async (req, res) => {
       SELECT 
         COUNT(DISTINCT c.id) as totalCategories,
         COUNT(DISTINCT CASE WHEN cm.status = 'active' THEN c.id END) as activeCategories,
-        SUM(cm.total_value) as totalValue,
-        AVG(cm.avg_margin) as avgMargin,
-        AVG(cm.growth_rate) as avgGrowth
+        COALESCE(SUM(cm.total_value), 0) as totalValue,
+        COALESCE(ROUND(AVG(NULLIF(cm.avg_margin, 0)), 1), 0) as avgMargin,
+        COALESCE(ROUND(AVG(NULLIF(cm.growth_rate, 0)), 1), 0) as avgGrowth
       FROM categories c
       LEFT JOIN category_metrics cm ON c.id = cm.category_id
     `);
 
     res.json({
-      categories,
+      categories: categories.map(cat => ({
+        ...cat,
+        product_count: parseInt(cat.product_count || 0),
+        total_value: parseFloat(cat.total_value || 0),
+        avg_margin: parseFloat(cat.avg_margin || 0),
+        turnover_rate: parseFloat(cat.turnover_rate || 0),
+        growth_rate: parseFloat(cat.growth_rate || 0)
+      })),
       parentCategories: parentCategories.map(p => p.parent_category),
-      stats: stats[0],
+      stats: {
+        ...stats[0],
+        totalValue: parseFloat(stats[0].totalValue || 0),
+        avgMargin: parseFloat(stats[0].avgMargin || 0),
+        avgGrowth: parseFloat(stats[0].avgGrowth || 0)
+      },
       pagination: {
         total: countResult[0].total,
         pages: Math.ceil(countResult[0].total / limit),