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)

.docker/selfhost/schema.json

@@ -864,22 +864,6 @@
         }
       }
     },
-    "customerIo": {
-      "type": "object",
-      "description": "Configuration for customerIo module",
-      "properties": {
-        "enabled": {
-          "type": "boolean",
-          "description": "Enable customer.io integration\n@default false",
-          "default": false
-        },
-        "token": {
-          "type": "string",
-          "description": "Customer.io token\n@default \"\"",
-          "default": ""
-        }
-      }
-    },
     "indexer": {
       "type": "object",
       "description": "Configuration for indexer module",
@@ -921,6 +905,22 @@
         }
       }
     },
+    "customerIo": {
+      "type": "object",
+      "description": "Configuration for customerIo module",
+      "properties": {
+        "enabled": {
+          "type": "boolean",
+          "description": "Enable customer.io integration\n@default false",
+          "default": false
+        },
+        "token": {
+          "type": "string",
+          "description": "Customer.io token\n@default \"\"",
+          "default": ""
+        }
+      }
+    },
     "oauth": {
       "type": "object",
       "description": "Configuration for oauth module",