🐛 Add Debug Logging for Thumbnails API Error

Added comprehensive debugging to identify why collection.id is undefined:
- Log identifier analysis (slug vs ID detection)
- Log which query path is taken (slug vs numeric ID)
- Log collection result structure and content
- Add validation for collection data before using collection.id
- Better error messages for debugging

This will help identify the root cause of the thumbnails API failure.

pages/api/collections/[identifier]/thumbnails.js

@@ -34,9 +34,12 @@ export default async function handler(req, res) {
     // Determine if identifier is a slug or numeric ID
     const isSlug = isValidSlug(identifier) || isNaN(parseInt(identifier));
     
+    console.log('🔍 Identifier analysis:', { identifier, isSlug, isValidSlug: isValidSlug(identifier), isNaN: isNaN(parseInt(identifier)) });
+    
     // Verify user has access to this collection
     let collectionResult;
     if (isSlug) {
+      console.log('🔍 Querying by slug:', identifier);
       collectionResult = await sql`
         SELECT c.*, cp.role as user_role
         FROM collections c
@@ -50,6 +53,7 @@ export default async function handler(req, res) {
       `;
     } else {
       const numericId = parseInt(identifier);
+      console.log('🔍 Querying by ID:', numericId);
       collectionResult = await sql`
         SELECT c.*, cp.role as user_role
         FROM collections c
@@ -67,7 +71,20 @@ export default async function handler(req, res) {
       return res.status(404).json({ error: 'Collection not found or access denied' });
     }
 
+    console.log('🔍 Collection result:', { 
+      identifier, 
+      isSlug, 
+      resultLength: collectionResult.length, 
+      collection: collectionResult[0] 
+    });
+
     const collection = collectionResult[0];
+    
+    // Add debugging and validation
+    if (!collection || !collection.id) {
+      console.error('Collection data invalid:', { collection, identifier, isSlug });
+      return res.status(500).json({ error: 'Collection data invalid' });
+    }
 
     // Get the top 5 rarest cards from the collection
     const thumbnailsResult = await sql`