feat(applications): remove the application custom settings tab (#22156)

## Summary

Removes the application **custom settings tab** feature. This is one
half of #22059, split out so it can be reviewed/merged independently
from the variable-types enrichment.

## Changes

- Remove the `SettingsApplicationCustomTab` component and its tab
entry/rendering in `SettingsApplicationDetails`.
- Stop syncing `settingsCustomTabFrontComponent` from application
manifests — `ApplicationManifestMigrationService` now only syncs the
default role.
- Deprecate the now-unused fields (kept for backward compatibility, no
longer read or synced):
- `ApplicationDTO.settingsCustomTabFrontComponentId` (GraphQL
`@deprecated`)
-
`ApplicationManifest.settingsCustomTabFrontComponentUniversalIdentifier`
- the `settingsCustomTabFrontComponentId` column comment on
`ApplicationEntity`

The DB column is intentionally **not dropped**, so existing
installations upgrade cleanly.

packages/twenty-front/src/generated-metadata/graphql.ts

@@ -302,6 +302,7 @@ export type Application = {
   objects: Array<Object>;
   packageJsonChecksum?: Maybe<Scalars['String']['output']>;
   packageJsonFileId?: Maybe<Scalars['UUID']['output']>;
+  /** @deprecated Custom settings tabs are no longer supported. This field is ignored. */
   settingsCustomTabFrontComponentId?: Maybe<Scalars['UUID']['output']>;
   universalIdentifier: Scalars['String']['output'];
   version?: Maybe<Scalars['String']['output']>;

packages/twenty-front/src/pages/settings/applications/SettingsApplicationDetails.tsx

@@ -22,7 +22,6 @@ import { type Manifest } from 'twenty-shared/application';
 import { SettingsPath } from 'twenty-shared/types';
 import { getSettingsPath, isDefined } from 'twenty-shared/utils';
 import {
-  IconApps,
   IconBox,
   IconCommand,
   IconGraph,
@@ -44,7 +43,6 @@ import { SettingsSectionSkeletonLoader } from '@/settings/components/SettingsSec
 import { CUSTOM_APPLICATION_ILLUSTRATIONS } from '~/pages/settings/applications/constants/CustomApplicationIllustrations';
 import { STANDARD_APPLICATION_ILLUSTRATIONS } from '~/pages/settings/applications/constants/StandardApplicationIllustrations';
 import { useFindApplicationConnectionProviders } from '~/pages/settings/applications/hooks/useFindApplicationConnectionProviders';
-import { SettingsApplicationCustomTab } from '~/pages/settings/applications/tabs/SettingsApplicationCustomTab';
 import { SettingsApplicationDetailAboutTab } from '~/pages/settings/applications/tabs/SettingsApplicationDetailAboutTab';
 import { SettingsApplicationDetailContentTab } from '~/pages/settings/applications/tabs/SettingsApplicationDetailContentTab';
 import { SettingsApplicationDetailSettingsTab } from '~/pages/settings/applications/tabs/SettingsApplicationDetailSettingsTab';
@@ -102,9 +100,6 @@ export const SettingsApplicationDetails = () => {
 
   const screenshots = getScreenshots();
 
-  const settingsCustomTabFrontComponentId =
-    application?.settingsCustomTabFrontComponentId;
-
   const { upgrade, isUpgrading } = useUpgradeApplication();
 
   const canInstallMarketplaceApps = useHasPermissionFlag(
@@ -245,9 +240,6 @@ export const SettingsApplicationDetails = () => {
         disabled: hasNothingToConfigure,
       };
     })(),
-    ...(isDefined(settingsCustomTabFrontComponentId)
-      ? [{ id: 'custom', title: t`Custom`, Icon: IconApps }]
-      : []),
   ];
 
   const renderActiveTabContent = () => {
@@ -312,16 +304,6 @@ export const SettingsApplicationDetails = () => {
         return (
           <SettingsApplicationDetailSettingsTab application={application} />
         );
-      case 'custom':
-        return isDefined(settingsCustomTabFrontComponentId) ? (
-          <SettingsApplicationCustomTab
-            settingsCustomTabFrontComponentId={
-              settingsCustomTabFrontComponentId
-            }
-          />
-        ) : (
-          <></>
-        );
       default:
         return <></>;
     }

packages/twenty-front/src/pages/settings/applications/tabs/SettingsApplicationCustomTab.tsx

@@ -1,32 +0,0 @@
-import { styled } from '@linaria/react';
-import { Suspense, lazy } from 'react';
-
-const FrontComponentRenderer = lazy(() =>
-  import('@/front-components/components/FrontComponentRenderer').then(
-    (module) => ({ default: module.FrontComponentRenderer }),
-  ),
-);
-
-const StyledContainer = styled.div`
-  height: 100%;
-  overflow: auto;
-  width: 100%;
-`;
-
-type SettingsApplicationCustomTabProps = {
-  settingsCustomTabFrontComponentId: string;
-};
-
-export const SettingsApplicationCustomTab = ({
-  settingsCustomTabFrontComponentId,
-}: SettingsApplicationCustomTabProps) => {
-  return (
-    <StyledContainer>
-      <Suspense fallback={null}>
-        <FrontComponentRenderer
-          frontComponentId={settingsCustomTabFrontComponentId}
-        />
-      </Suspense>
-    </StyledContainer>
-  );
-};