fix(migrations): revert to correct migration v4.0-to-v4.1

The migration was correct as v4.0→v4.1. Config version goes from 4.0 to 4.1
when thresholds are moved to actions. The original error was not the migration
but the ups-handler.ts bug (already fixed in v4.2.1).

User's config shows version "4.1" with actions already present, confirming
the migration ran successfully.

ts/migrations/migration-runner.ts

@@ -1,7 +1,7 @@
 import { BaseMigration } from './base-migration.ts';
 import { MigrationV1ToV2 } from './migration-v1-to-v2.ts';
 import { MigrationV3ToV4 } from './migration-v3-to-v4.ts';
-import { MigrationV4_1ToV4_2 } from './migration-v4.1-to-v4.2.ts';
+import { MigrationV4_0ToV4_1 } from './migration-v4.0-to-v4.1.ts';
 import { logger } from '../logger.ts';
 
 /**
@@ -18,7 +18,7 @@ export class MigrationRunner {
     this.migrations = [
       new MigrationV1ToV2(),
       new MigrationV3ToV4(),
-      new MigrationV4_1ToV4_2(),
+      new MigrationV4_0ToV4_1(),
       // Add future migrations here (v4.3, v4.4, etc.)
     ];