feat: manufacturer service with list, get, create

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

tests/helpers/db.ts

@@ -25,6 +25,8 @@ const TRUNCATE_TABLES = [
 	"setups",
 	"thread_candidates",
 	"threads",
+	"community_prices",
+	"market_prices",
 	"items",
 	"global_item_tags",
 	"global_items",
@@ -35,6 +37,7 @@ const TRUNCATE_TABLES = [
 	"api_keys",
 	"settings",
 	"categories",
+	"manufacturers",
 	"users",
 ];