rebrand to useSend (#210)

apps/web/prisma/migrations/20250901091500_add_dkim_selector/migration.sql

@@ -0,0 +1,9 @@
+-- Add dkimSelector column (nullable) with default 'usesend'
+ALTER TABLE "Domain" ADD COLUMN "dkimSelector" TEXT;
+
+-- Set existing rows to 'unsend' to preserve current selector
+UPDATE "Domain" SET "dkimSelector" = 'unsend' WHERE "dkimSelector" IS NULL;
+
+-- Set default for new rows to 'usesend'
+ALTER TABLE "Domain" ALTER COLUMN "dkimSelector" SET DEFAULT 'usesend';
+