fix: migrate webhook and API key REST endpoints to core schema (#13318)

## Problem
After migrating webhooks and API keys from workspace to core level, REST
API endpoints were still creating entities in workspace schema
(`workspace_*`) instead of core schema, causing webhooks to not fire.

## Solution
- Added dedicated REST controllers for webhooks (`/rest/webhooks`) and
API keys (`/rest/apiKeys`)
- Updated dynamic controller to block workspace-gated entities from
being processed
- Fixed OpenAPI documentation to exclude these endpoints from playground
- Ensured return formats match GraphQL resolvers exactly

## Testing
✅ All endpoints tested with provided auth token - webhooks and API keys
now correctly stored in `core` schema

packages/twenty-server/src/engine/twenty-orm/interfaces/gate.interface.ts

@@ -1,5 +1,5 @@
 export interface Gate {
   featureFlag: string;
   excludeFromDatabase?: boolean;
-  excludeFromGraphQL?: boolean;
+  excludeFromWorkspaceApi?: boolean;
 }