feat(server): add doc keyword search tool (#12837)

close AI-185

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

- **New Features**
- Introduced a keyword-based document search tool, allowing users to
search for relevant documents within their workspace using keywords.
- Search results include document titles, summaries, and direct links,
enhancing document discovery and navigation.
- **Bug Fixes**
  - None.
- **Tests**
- Added new tests to verify document search by IDs and by keywords,
ensuring accurate and reliable search functionality.
- **Documentation**
  - None.
- **Chores**
- Updated configuration file organization for improved clarity; no
changes to functionality.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->








#### PR Dependency Tree


* **PR #12867**
  * **PR #12863**
    * **PR #12837** 👈

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

packages/frontend/admin/src/config.json

@@ -262,16 +262,6 @@
       "desc": "The config for the storage provider."
     }
   },
-  "customerIo": {
-    "enabled": {
-      "type": "Boolean",
-      "desc": "Enable customer.io integration"
-    },
-    "token": {
-      "type": "String",
-      "desc": "Customer.io token"
-    }
-  },
   "indexer": {
     "enabled": {
       "type": "Boolean",
@@ -310,6 +300,16 @@
       "desc": "Number of workspaces automatically indexed per batch"
     }
   },
+  "customerIo": {
+    "enabled": {
+      "type": "Boolean",
+      "desc": "Enable customer.io integration"
+    },
+    "token": {
+      "type": "String",
+      "desc": "Customer.io token"
+    }
+  },
   "oauth": {
     "providers.google": {
       "type": "Object",