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/admin-panel/config-variables/components/SettingsAdminConfigVariables.tsx

@@ -13,7 +13,7 @@ import { Section } from 'twenty-ui/layout';
 import {
   ConfigSource,
   useGetConfigVariablesGroupedQuery,
-} from '~/generated/graphql';
+} from '~/generated-metadata/graphql';
 import { ConfigVariableSearchInput } from './ConfigVariableSearchInput';
 
 const StyledControlsContainer = styled.div`