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/modules/api-key/standard-objects/api-key.workspace-entity.ts

@@ -24,7 +24,7 @@ import { STANDARD_OBJECT_IDS } from 'src/engine/workspace-manager/workspace-sync
 @WorkspaceGate({
   featureFlag: 'IS_WORKSPACE_API_KEY_WEBHOOK_GRAPHQL_ENABLED',
   excludeFromDatabase: false,
-  excludeFromGraphQL: true,
+  excludeFromWorkspaceApi: true,
 })
 export class ApiKeyWorkspaceEntity extends BaseWorkspaceEntity {
   @WorkspaceField({

packages/twenty-server/src/modules/webhook/standard-objects/webhook.workspace-entity.ts

@@ -25,7 +25,7 @@ import { STANDARD_OBJECT_IDS } from 'src/engine/workspace-manager/workspace-sync
 @WorkspaceGate({
   featureFlag: 'IS_WORKSPACE_API_KEY_WEBHOOK_GRAPHQL_ENABLED',
   excludeFromDatabase: false,
-  excludeFromGraphQL: true,
+  excludeFromWorkspaceApi: true,
 })
 export class WebhookWorkspaceEntity extends BaseWorkspaceEntity {
   @WorkspaceField({