feat(server): improve indexer perf (#15512)

#### PR Dependency Tree


* **PR #15512** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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

## Summary by CodeRabbit

* **New Features**
* Search now supports generation-based indexing with embedded and remote
providers.
* Added automatic search reconciliation and improved handling of
document, workspace, and permission changes.
* Added clearer search status errors for unavailable, syncing, unready,
or failed indexes.
* Added Manticore Search end-to-end support and provider-specific search
behavior.

* **Improvements**
* Search and aggregate pagination now report returned results and
continuation status more accurately.
* Improved permission filtering to prevent inaccessible documents from
appearing in results.
  * Admin provider selection now consistently enables indexing.

* **Documentation**
* Clarified search pagination, aggregation counts, provider
configuration, and end-to-end setup.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/e2e/remote-provider/README.md

@@ -0,0 +1,39 @@
+# Remote provider E2E
+
+These tests exercise the Elasticsearch-compatible provider over HTTP against a
+local OpenSearch instance. Toxiproxy is included so the lease test can inject
+provider latency without changing production code.
+
+```bash
+docker compose -f packages/backend/server/e2e/remote-provider/compose.yml up -d --wait
+
+DATABASE_URL=postgresql://ds:ds@localhost:55432/affine_rfc6_remote_e2e \
+yarn workspace @affine/server prisma migrate deploy
+```
+
+Configure `packages/backend/server/config.json` with:
+
+```json
+{
+  "indexer": {
+    "enabled": true,
+    "provider": {
+      "type": "elasticsearch",
+      "endpoint": "http://127.0.0.1:8666"
+    }
+  }
+}
+```
+
+Then run:
+
+```bash
+DATABASE_URL=postgresql://ds:ds@localhost:55432/affine_rfc6_remote_e2e \
+yarn af server e2e src/__tests__/e2e/indexer/remote-provider.spec.ts
+
+docker compose -f packages/backend/server/e2e/remote-provider/compose.yml down -v
+```
+
+The suite uses a disposable PostgreSQL database and creates generation-specific
+indices. It directly deletes or mutates provider rows only as a fault-injection
+fixture; production code still repairs them through the normal reconcile path.