feat: enhance purchase intentions with chat integration and offer tracking

- Added MongoDB chat/message integration for seller responses
- Improved seller response validation and default messaging
- Integrated automatic chat creation/update when responding to intentions
- Added highest custom offer fields to listing queries and models
- Enhanced listing data with top offer information for buyers

lib/db/migrations/run-migrations.ts

@@ -1,4 +1,4 @@
-/**
+/**
  * Script de execução de migrations
  * Executa todas as migrations SQL em ordem
  */
@@ -39,6 +39,7 @@ const MIGRATIONS = [
   "017_add_items_foreign_key.sql",
   "018_migrate_listings_to_unified_items.sql",
   "019_subscription_tiers.sql",
+  "020_purchase_intentions_custom_offer.sql",
 ];
 
 async function runMigrations() {