Refactor OIDC provider migration to be idempotent

prisma/migrations/20251103162035_add_oidc_provider/migration.sql

@@ -1,2 +1,7 @@
--- AlterEnum
-ALTER TYPE "Provider" ADD VALUE 'OIDC';
+-- AlterEnum (idempotent - only add if not exists)
+DO $$
+BEGIN
+    IF NOT EXISTS (SELECT 1 FROM pg_enum WHERE enumlabel = 'OIDC' AND enumtypid = (SELECT oid FROM pg_type WHERE typname = 'Provider')) THEN
+        ALTER TYPE "Provider" ADD VALUE 'OIDC';
+    END IF;
+END $$;

prisma/migrations/20251103162035_added_oidc_to_provider/migration.sql

@@ -1,2 +0,0 @@
--- AlterEnum
-ALTER TYPE "Provider" ADD VALUE 'OIDC';