fix(server): use new LocalWorkspace ServerFeature instead (#13091)

keep compatibility

close AF-2720



#### PR Dependency Tree


* **PR #13091** 👈

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

## Summary by CodeRabbit

* **New Features**
* Added a new `LocalWorkspace` feature flag to server configuration,
enabling more flexible feature management.

* **Deprecations**
* The `allowGuestDemoWorkspace` flag is now deprecated and will be
removed in version 0.25.0. Please use the `features` array for feature
checks instead.

* **Bug Fixes**
* Updated UI and logic throughout the app to rely on the new
`LocalWorkspace` feature flag rather than the deprecated boolean flag.

* **Chores**
* Removed references to `allowGuestDemoWorkspace` from configuration,
queries, and type definitions for improved consistency.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->


#### PR Dependency Tree


* **PR #13091** 👈

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

packages/backend/server/src/schema.gql

@@ -1760,7 +1760,7 @@ enum SearchTable {
 
 type ServerConfigType {
   """Whether allow guest users to create demo workspaces."""
-  allowGuestDemoWorkspace: Boolean!
+  allowGuestDemoWorkspace: Boolean! @deprecated(reason: "This field is deprecated, please use `features` instead. Will be removed in 0.25.0")
 
   """fetch latest available upgradable release of server"""
   availableUpgrade: ReleaseVersionType
@@ -1802,6 +1802,7 @@ enum ServerFeature {
   Copilot
   CopilotEmbedding
   Indexer
+  LocalWorkspace
   OAuth
   Payment
 }