feat(server): add cloud indexer with Elasticsearch and Manticoresearch providers (#11835)

close CLOUD-137

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

- **New Features**
  - Introduced advanced workspace-scoped search and aggregation capabilities with support for complex queries, highlights, and pagination.
  - Added pluggable search providers: Elasticsearch and Manticoresearch.
  - New GraphQL queries, schema types, and resolver support for search and aggregation.
  - Enhanced configuration options for search providers in self-hosted and cloud deployments.
  - Added Docker Compose services and environment variables for Elasticsearch and Manticoresearch.
  - Integrated indexer service into deployment and CI workflows.

- **Bug Fixes**
  - Improved error handling with new user-friendly error messages for search provider and indexer issues.

- **Documentation**
  - Updated configuration examples and environment variable references for indexer and search providers.

- **Tests**
  - Added extensive end-to-end and provider-specific tests covering indexing, searching, aggregation, deletion, and error cases.
  - Included snapshot tests and test fixtures for search providers.

- **Chores**
  - Updated deployment scripts, Helm charts, and Kubernetes manifests to include indexer-related environment variables and secrets.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/app.module.ts

@@ -49,6 +49,7 @@ import { CaptchaModule } from './plugins/captcha';
 import { CopilotModule } from './plugins/copilot';
 import { CustomerIoModule } from './plugins/customerio';
 import { GCloudModule } from './plugins/gcloud';
+import { IndexerModule } from './plugins/indexer';
 import { LicenseModule } from './plugins/license';
 import { OAuthModule } from './plugins/oauth';
 import { PaymentModule } from './plugins/payment';
@@ -146,7 +147,8 @@ export function buildAppModule(env: Env) {
     // enable schedule module on graphql server and doc service
     .useIf(
       () => env.flavors.graphql || env.flavors.doc,
-      ScheduleModule.forRoot()
+      ScheduleModule.forRoot(),
+      IndexerModule
     )
 
     // auth