fix(migration): remap firecrawl rows in the down migration

The down migration narrows the searchengine_type enum by casting the
engine column to a new enum that no longer contains 'firecrawl'. Any row
logged with 'firecrawl' would make that cast fail, so a rollback errors out
once the engine has been used. Remap those rows to 'tavily' before the cast
so the down migration is safe on real data.

backend/migrations/sql/20260716_120000_add_firecrawl_search_type.sql

@@ -40,6 +40,12 @@ CREATE TYPE SEARCHENGINE_TYPE_NEW AS ENUM (
   'sploitus'
 );
 
+-- Remap any rows logged with the removed value so the narrowing cast below
+-- cannot fail; 'firecrawl' is a content-rich search engine like 'tavily'.
+UPDATE searchlogs
+    SET engine = 'tavily'
+    WHERE engine = 'firecrawl';
+
 -- Update the searchlogs table to use the reverted enum type
 ALTER TABLE searchlogs
     ALTER COLUMN engine TYPE SEARCHENGINE_TYPE_NEW USING engine::text::SEARCHENGINE_TYPE_NEW;