feat: bump typescript (#14507)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Chores**
  * Upgraded TypeScript toolchain to v5.9.3 across packages and tooling.
* Removed legacy ts-node and migrated developer tooling to newer
runtimes (tsx/SWC) where applicable.
* **Documentation**
* Updated developer CLI docs and runtime behavior notes to reflect the
new loader/runtime for running TypeScript files; no changes to public
APIs or end-user behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/calendar/__tests__/caldav.spec.ts

@@ -9,7 +9,7 @@ import { CryptoHelper, GraphqlBadRequest, Mutex } from '../../../base';
 import { ConfigModule } from '../../../base/config';
 import { ServerConfigModule } from '../../../core/config';
 import { Models } from '../../../models';
-import { CalendarModule } from '..';
+import { CalendarModule } from '../index';
 import {
   CalDAVProvider,
   CalendarProviderFactory,

packages/backend/server/src/plugins/calendar/__tests__/service.spec.ts

@@ -13,7 +13,7 @@ import type {
   UpsertCalendarSubscriptionInput,
 } from '../../../models';
 import { Models } from '../../../models';
-import { CalendarModule } from '..';
+import { CalendarModule } from '../index';
 import {
   CalendarProvider,
   CalendarProviderFactory,