Add FIND on GoogleCampaignID field as fallback for lead matching

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

airtable_client.py

@@ -344,6 +344,7 @@ class AirtableClient:
             f"AND("
             f"OR("
             f"{{GACampaignID}}='{campaign_id}',"
+            f"FIND('{campaign_id}',{{GoogleCampaignID}}),"
             f"FIND('gad_campaignid={campaign_id}',{{attr_referer}})"
             f"),"
             f"{{attr_utm_medium}}='paid_search',"