fix: protect products with history from being overwritten by Dropbox sync

Products that have entries in products_history were edited at some point.
If their status was accidentally reset to 'excel', the sync would overwrite
their data. Now also check products_history to build the protected set.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/dropbox-sync.js

@@ -44,14 +44,21 @@ export default async function handler(req, res) {
     const { data: existingProducts } = await supabase
       .from('products')
       .select('product_id, status');
-    
-    // Only skip if status is 'edited' or 'pending' (manual edits)
+
+    // Protect products with status 'edited' or 'pending'
     const manuallyEditedIds = new Set(
       (existingProducts || [])
         .filter(p => p.status === 'edited' || p.status === 'pending')
         .map(p => p.product_id)
     );
 
+    // Also protect any product that has history entries — they were edited at some point.
+    // If their status was accidentally reset to 'excel', this restores protection.
+    const { data: historyProducts } = await supabase
+      .from('products_history')
+      .select('product_id');
+    (historyProducts || []).forEach(h => manuallyEditedIds.add(h.product_id));
+
     const productsToUpsert = [];
     for (const row of rows) {
       const productId = String(row[articleNoIdx]);