Fix image preview URLs in admin panel

- Use VITE_API_URL environment variable instead of hardcoded localhost:8000
- Fixes broken image previews for both category and product uploads
- Properly constructs backend URL from API URL

frontend/src/pages/Admin.jsx

@@ -167,6 +167,10 @@ export default function Admin() {
     const newImages = [...uploadedImages]
 
     try {
+      // Get backend URL from environment
+      const apiUrl = import.meta.env.VITE_API_URL || 'http://localhost:8000/api'
+      const backendUrl = apiUrl.replace('/api', '') // Remove /api suffix to get base URL
+
       for (let i = 0; i < files.length; i++) {
         const file = files[i]
         const formDataUpload = new FormData()
@@ -179,7 +183,9 @@ export default function Admin() {
         })
 
         // Add the full URL
-        const imageUrl = `http://localhost:8000${response.data.url}`
+        const imageUrl = response.data.url.startsWith('http') 
+          ? response.data.url 
+          : `${backendUrl}${response.data.url}`
         newImages.push(imageUrl)
       }
 
@@ -339,9 +345,11 @@ export default function Admin() {
         headers: { 'Content-Type': 'multipart/form-data' }
       })
       // Prepend backend URL for image display
+      const apiUrl = import.meta.env.VITE_API_URL || 'http://localhost:8000/api'
+      const backendUrl = apiUrl.replace('/api', '') // Remove /api suffix to get base URL
       const imageUrl = response.data.url.startsWith('http') 
         ? response.data.url 
-        : `http://localhost:8000${response.data.url}`
+        : `${backendUrl}${response.data.url}`
       setCategoryFormData({ ...categoryFormData, image: imageUrl })
       setToast({ type: 'success', message: 'Image uploaded successfully!' })
     } catch (error) {