chore(front): move mocked-metadata helpers under src/testing (#20341)

## Summary

Follow-up to #20308. After that PR, production code no longer loads
mocked metadata when the user is unauthenticated. The remaining
mocked-metadata helpers (`useLoadMockedMetadata`,
`preloadMockedMetadata`) are now only consumed by Storybook decorators,
so move them next to the other testing-only utilities to make their
scope explicit and prevent accidental re-introduction of a runtime
dependency on mocks.

- `src/modules/metadata-store/hooks/useLoadMockedMetadata.ts`
  → `src/testing/hooks/useLoadMockedMetadata.ts`
- `src/modules/metadata-store/utils/preloadMockedMetadata.ts`
  → `src/testing/utils/preloadMockedMetadata.ts`

The three Storybook decorator imports
(`MockedMetadataLoadEffect`, `ObjectMetadataItemsDecorator`,
`WorkflowStepDecorator`) are updated to the new `~/testing/...` paths.

No runtime behavior change.

## Test plan

- [x] `npx oxlint --type-aware -c .oxlintrc.json` on touched files —
clean
- [x] `npx prettier --check` on touched files — clean
- [ ] CI: storybook, unit tests, e2e tests

packages/twenty-front/src/testing/decorators/MockedMetadataLoadEffect.tsx

@@ -1,4 +1,4 @@
-import { useLoadMockedMetadata } from '@/metadata-store/hooks/useLoadMockedMetadata';
+import { useLoadMockedMetadata } from '~/testing/hooks/useLoadMockedMetadata';
 import { isMinimalMetadataReadyState } from '@/metadata-store/states/isMinimalMetadataReadyState';
 import { metadataStoreState } from '@/metadata-store/states/metadataStoreState';
 import { useAtomFamilyStateValue } from '@/ui/utilities/state/jotai/hooks/useAtomFamilyStateValue';

packages/twenty-front/src/testing/decorators/ObjectMetadataItemsDecorator.tsx

@@ -7,7 +7,7 @@ import { currentWorkspaceMemberState } from '@/auth/states/currentWorkspaceMembe
 import { useSetAtomState } from '@/ui/utilities/state/jotai/hooks/useSetAtomState';
 import { useAtomStateValue } from '@/ui/utilities/state/jotai/hooks/useAtomStateValue';
 import { PreComputedChipGeneratorsProvider } from '@/object-metadata/components/PreComputedChipGeneratorsProvider';
-import { useLoadMockedMetadata } from '@/metadata-store/hooks/useLoadMockedMetadata';
+import { useLoadMockedMetadata } from '~/testing/hooks/useLoadMockedMetadata';
 import { objectMetadataItemsSelector } from '@/object-metadata/states/objectMetadataItemsSelector';
 import { getRecordFromRecordNode } from '@/object-record/cache/utils/getRecordFromRecordNode';
 import { type WorkspaceMember } from '@/workspace-member/types/WorkspaceMember';

packages/twenty-front/src/testing/decorators/WorkflowStepDecorator.tsx

@@ -1,6 +1,6 @@
 import { sidePanelWorkflowIdComponentState } from '@/side-panel/pages/workflow/states/sidePanelWorkflowIdComponentState';
 import { SidePanelPageComponentInstanceContext } from '@/side-panel/states/contexts/SidePanelPageComponentInstanceContext';
-import { useLoadMockedMetadata } from '@/metadata-store/hooks/useLoadMockedMetadata';
+import { useLoadMockedMetadata } from '~/testing/hooks/useLoadMockedMetadata';
 import { flowComponentState } from '@/workflow/states/flowComponentState';
 import { workflowVisualizerWorkflowIdComponentState } from '@/workflow/states/workflowVisualizerWorkflowIdComponentState';
 import { workflowVisualizerWorkflowRunIdComponentState } from '@/workflow/states/workflowVisualizerWorkflowRunIdComponentState';

packages/twenty-front/src/testing/hooks/useLoadMockedMetadata.ts

@@ -1,11 +1,11 @@
 import { useUpdateMetadataStoreDraft } from '@/metadata-store/hooks/useUpdateMetadataStoreDraft';
 import { metadataStoreState } from '@/metadata-store/states/metadataStoreState';
+import { useStore } from 'jotai';
+import { useCallback } from 'react';
 import {
   preloadMockedMetadata,
   type PreloadedMockedMetadata,
-} from '@/metadata-store/utils/preloadMockedMetadata';
-import { useStore } from 'jotai';
-import { useCallback } from 'react';
+} from '~/testing/utils/preloadMockedMetadata';
 
 const MOCKED_COLLECTION_HASH = 'mocked';