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/pages/onboarding/ChooseYourPlan.tsx

@@ -27,7 +27,7 @@ import {
   BillingPlanKey,
   BillingPriceLicensedDto,
   useBillingBaseProductPricesQuery,
-} from '~/generated/graphql';
+} from '~/generated-metadata/graphql';
 
 const StyledSubscriptionContainer = styled.div<{
   withLongerMarginBottom: boolean;