refactor: rename ObjectMetadataItem to EnrichedObjectMetadataItem and clean up metadata flows (#18830)

## Summary

- Renames `ObjectMetadataItem` to `EnrichedObjectMetadataItem` across
the entire frontend (~440 files) to clarify that this type includes
derived fields (`readableFields`, `updatableFields`, nested `fields[]`,
`indexMetadatas[]`) computed at read time from the metadata store
- Creates `splitObjectMetadataGqlResponse` that goes directly from a
GraphQL `ObjectMetadataItemsQuery` response to flat store items
(combining the old
`mapPaginatedObjectMetadataItemsToObjectMetadataItems` +
`splitObjectMetadataItemWithRelated` two-step flow into one call)
- Removes `ObjectMetadataItemWithRelated` type and all "WithRelated"
naming
- Renames `generatedMockObjectMetadataItems` to
`generateTestEnrichedObjectMetadataItemsMock` to make it clear this is
test-only enriched data
- Deletes `useLoadMockedObjectMetadataItems` hook (consolidated into
`useLoadMockedMinimalMetadata`)
- Ensures nothing destined for the metadata store computes
`readableFields`/`updatableFields` (preventing the localStorage bloat
from #18809)

## Type hierarchy (before → after)

**Before:**
```
ObjectMetadataItemsQuery → mapPaginated → ObjectMetadataItemWithRelated → enrich → ObjectMetadataItem
                                        → split → FlatObjectMetadataItem (store)
```

**After:**
```
ObjectMetadataItemsQuery → splitObjectMetadataGqlResponse → FlatObjectMetadataItem (store)
                         → mapPaginated + enrich (tests only) → EnrichedObjectMetadataItem
```

## Test plan

- [x] `npx nx typecheck twenty-front` passes
- [x] `npx nx test twenty-front` passes (767 suites, 4505 tests)
- [x] `npx nx lint twenty-front` passes
- [ ] CI checks pass


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packages/twenty-front/src/modules/settings/data-model/objects/components/SettingsDataModelObjectSummary.tsx

@@ -2,7 +2,7 @@ import { t } from '@lingui/core/macro';
 import { styled } from '@linaria/react';
 import { useContext } from 'react';
 
-import { type ObjectMetadataItem } from '@/object-metadata/types/ObjectMetadataItem';
+import { type EnrichedObjectMetadataItem } from '@/object-metadata/types/EnrichedObjectMetadataItem';
 import {
   IconBox,
   OverflowingTextWithTooltip,
@@ -14,7 +14,7 @@ import { ThemeContext, themeCssVariables } from 'twenty-ui/theme-constants';
 export type SettingsDataModelObjectPreviewProps = {
   className?: string;
   objectMetadataItems: Pick<
-    ObjectMetadataItem,
+    EnrichedObjectMetadataItem,
     'icon' | 'labelSingular' | 'labelPlural' | 'isCustom' | 'isRemote'
   >[];
   pluralizeLabel?: boolean;
@@ -55,7 +55,7 @@ const StyledSeparator = styled.div`
 
 type SettingsDataModelObjectPreviewItemProps = {
   objectMetadataItem: Pick<
-    ObjectMetadataItem,
+    EnrichedObjectMetadataItem,
     'icon' | 'labelSingular' | 'labelPlural' | 'isCustom' | 'isRemote'
   >;
   pluralizeLabel: boolean;