Replace sign-in mocked metadata with hardcoded BackgroundMock (#20308)

## Summary

When the user is logged out, we render the auth modal on top of a sample
table to make the empty page feel alive. So far this was achieved by
**loading a full set of mocked object / field / view / navigation-menu
metadata into the runtime metadata store** and then mounting the real
`RecordTable` and `AppNavigationDrawer` behind the modal. This had a few
downsides:

- Significant bundle weight pulled in for unauthenticated users (mocked
GraphQL fixtures + the real `RecordTable` virtualization stack).
- Plenty of code paths that had to know about the "showAuthModal" case
(`useRecordIndexTableQuery`, `useTriggerInitialRecordTableDataLoad`,
`MainContextStoreProvider`, `IsMinimalMetadataReadyEffect`...).
- Any change to metadata-store internals or to the record-table runtime
risked breaking the logged-out background.

This PR replaces the entire flow with a small, self-contained
`BackgroundMock` component tree that **does not consume any metadata**
and **does not load any mocked metadata at runtime**.

### What changed

- New module under `sign-in-background-mock`:
- `BackgroundMockPage` + `BackgroundMockViewBar` + `BackgroundMockTable`
+ `BackgroundMockTableRow` render a hardcoded "Companies" table that
visually mirrors the real one.
- `BackgroundMockNavigationDrawer` renders a hardcoded sidebar with
People / Companies / Opportunities / Tasks / Notes (with their standard
colors).
- Hardcoded constants in `BackgroundMockCompanies.ts`,
`BackgroundMockColumns.ts`, `BackgroundMockNavigationItems.ts`.
- `MinimalMetadataLoadEffect` no longer calls `loadMockedMetadataAtomic`
for unauthenticated users — it just doesn't load anything.
- `IsMinimalMetadataReadyEffect` now reports ready immediately when
there is no access token pair, so the skeleton loader doesn't hang
waiting for metadata that will never come.
- `MainContextStoreProvider`, `useRecordIndexTableQuery`, and
`useTriggerInitialRecordTableDataLoad` drop their `showAuthModal`
branches — the real `RecordTable` is no longer mounted behind the modal.
- `DefaultLayout` and `NotFound` now lazily load `BackgroundMockPage` /
`BackgroundMockNavigationDrawer` instead of the deleted
`SignInBackgroundMockPage` / `SignInAppNavigationDrawerMock`.
- Removed: `SignInBackgroundMockPage`, `SignInBackgroundMockContainer`,
`SignInBackgroundMockContainerEffect`, `SignInAppNavigationDrawerMock`,
`SignInBackgroundMockColumnDefinitions`,
`SignInBackgroundMockCompanies`, `SignInBackgroundMockViewFields`.

`useLoadMockedMetadata` and `preloadMockedMetadata` are kept on purpose:
Storybook decorators (`ObjectMetadataItemsDecorator`,
`WorkflowStepDecorator`) still rely on the mocked metadata fixtures, but
**production** unauthenticated runtime no longer touches them.

### Visual parity

Side-by-side at 1440×900 on `/sign-in`:

**Before** (loads mocked metadata + real RecordTable):

![before](https://github.com/user-attachments/assets/before-placeholder)

**After** (purely hardcoded BackgroundMock):

![after](https://github.com/user-attachments/assets/after-placeholder)

## Test plan

- [ ] `npx nx typecheck twenty-front` ✅ (passes locally)
- [ ] `npx nx lint:diff-with-main twenty-front` ✅ (oxlint + prettier
clean)
- [ ] `npx jest useRecordIndexTableQuery` ✅
- [ ] Manually verify `/sign-in` renders the table + nav drawer behind
the modal
- [ ] Manually verify `/not-found` still renders the background
- [ ] Verify CI: storybook, unit tests, e2e tests

packages/twenty-front/src/modules/metadata-store/effect-components/IsMinimalMetadataReadyEffect.tsx

@@ -28,21 +28,24 @@ export const IsMinimalMetadataReadyEffect = () => {
   );
 
   useEffect(() => {
+    if (!hasAccessTokenPair) {
+      setIsMinimalMetadataReady(true);
+      return;
+    }
+
     const hasActiveWorkspace = isWorkspaceActiveOrSuspended(currentWorkspace);
 
     const areObjectsLoaded = metadataStore.status === 'up-to-date';
     const areViewsLoaded = metadataStoreViews.status === 'up-to-date';
 
-    const isReady = !areObjectsLoaded
-      ? false
-      : !hasAccessTokenPair ||
-        (isDefined(currentUser) && (!hasActiveWorkspace || areViewsLoaded));
-
     if (!areObjectsLoaded) {
       setIsMinimalMetadataReady(false);
       return;
     }
 
+    const isReady =
+      isDefined(currentUser) && (!hasActiveWorkspace || areViewsLoaded);
+
     if (isReady) {
       setIsMinimalMetadataReady(true);
     }

packages/twenty-front/src/modules/metadata-store/effect-components/MinimalMetadataLoadEffect.tsx

@@ -2,70 +2,41 @@ import { useHasAccessTokenPair } from '@/auth/hooks/useHasAccessTokenPair';
 import { currentWorkspaceState } from '@/auth/states/currentWorkspaceState';
 import { isCurrentUserLoadedState } from '@/auth/states/isCurrentUserLoadedState';
 import { useLoadMinimalMetadata } from '@/metadata-store/hooks/useLoadMinimalMetadata';
-import { useLoadMockedMetadata } from '@/metadata-store/hooks/useLoadMockedMetadata';
 import { useLoadStaleMetadataEntities } from '@/metadata-store/hooks/useLoadStaleMetadataEntities';
 import { metadataLoadedVersionState } from '@/metadata-store/states/metadataLoadedVersionState';
 import { useAtomStateValue } from '@/ui/utilities/state/jotai/hooks/useAtomStateValue';
 import { useEffect, useState } from 'react';
 import { isWorkspaceActiveOrSuspended } from 'twenty-shared/workspace';
 
-type LoadedState = 'none' | 'mocked' | 'real';
-
-const computeDesiredLoadState = (
-  hasAccessTokenPair: boolean,
-  isActiveWorkspace: boolean,
-): LoadedState => {
-  if (hasAccessTokenPair && isActiveWorkspace) {
-    return 'real';
-  }
-
-  return 'mocked';
-};
-
 export const MinimalMetadataLoadEffect = () => {
   const hasAccessTokenPair = useHasAccessTokenPair();
   const isCurrentUserLoaded = useAtomStateValue(isCurrentUserLoadedState);
   const currentWorkspace = useAtomStateValue(currentWorkspaceState);
   const metadataLoadedVersion = useAtomStateValue(metadataLoadedVersionState);
-  const [lastMetadataLoadData, setLastMetadataLoadData] = useState<{
-    state: LoadedState;
-    version: number;
-  }>({ state: 'none', version: -1 });
+  const [lastLoadedVersion, setLastLoadedVersion] = useState<number>(-1);
 
   const { loadMinimalMetadata } = useLoadMinimalMetadata();
-  const { loadMockedMetadataAtomic } = useLoadMockedMetadata();
   const { loadStaleMetadataEntities } = useLoadStaleMetadataEntities();
 
   const isActiveWorkspace = isWorkspaceActiveOrSuspended(currentWorkspace);
-
-  const desiredLoadState = computeDesiredLoadState(
-    hasAccessTokenPair,
-    isActiveWorkspace,
-  );
+  const shouldLoadRealMetadata = hasAccessTokenPair && isActiveWorkspace;
 
   useEffect(() => {
     if (!isCurrentUserLoaded) {
       return;
     }
 
-    const versionChanged =
-      metadataLoadedVersion !== lastMetadataLoadData.version;
-
-    if (!versionChanged && lastMetadataLoadData.state === desiredLoadState) {
+    if (!shouldLoadRealMetadata) {
       return;
     }
 
-    setLastMetadataLoadData({
-      state: desiredLoadState,
-      version: metadataLoadedVersion,
-    });
+    if (metadataLoadedVersion === lastLoadedVersion) {
+      return;
+    }
+
+    setLastLoadedVersion(metadataLoadedVersion);
 
     const performLoad = async () => {
-      if (desiredLoadState === 'mocked') {
-        await loadMockedMetadataAtomic();
-        return;
-      }
-
       const result = await loadMinimalMetadata();
 
       if (result?.staleEntityKeys && result.staleEntityKeys.length > 0) {
@@ -76,13 +47,10 @@ export const MinimalMetadataLoadEffect = () => {
     performLoad();
   }, [
     isCurrentUserLoaded,
-    hasAccessTokenPair,
-    isActiveWorkspace,
-    desiredLoadState,
-    lastMetadataLoadData,
+    shouldLoadRealMetadata,
+    lastLoadedVersion,
     metadataLoadedVersion,
     loadMinimalMetadata,
-    loadMockedMetadataAtomic,
     loadStaleMetadataEntities,
   ]);