Separate system operations from core objects in GraphQL endpoints (#12977)

Moves system-level operations (auth, billing, admin) to use the
/metadata endpoint instead of /graphql.

This cleans up the endpoint separation so /graphql is purely for core
objects (Company, People, etc.) and /metadata handles all system
operations.

Part of prep work for webhook/API key core migration.

packages/twenty-front/src/modules/settings/data-model/utils/__tests__/isSelectOptionDefaultValue.test.ts

@@ -1,4 +1,4 @@
-import { FieldMetadataType } from '~/generated/graphql';
+import { FieldMetadataType } from '~/generated-metadata/graphql';
 
 import { isSelectOptionDefaultValue } from '../isSelectOptionDefaultValue';