fix: restore isCustom gate in metadata label resolvers (#21432)

## Context

#21228 removed the stored `isCustom` column and, with it, the `isCustom`
early-return in `resolveObjectMetadataStandardOverride` /
`resolveFieldMetadataStandardOverride`, on the assumption that falling
through the `standardOverrides` checks was equivalent.

It isn't: custom object/field labels now reach the Lingui lookup. A
custom label that collides with a standard catalog string (e.g. a custom
field labeled "Status") gets translated for non-English locales against
the user's intent, and every other custom label pays a hash + catalog
miss — and, in production, an "Uncompiled message detected" warning
(#21415) — on each metadata resolution.

## Fix

Restore the gate. `isCustom` is no longer stored, so call sites that
build the resolver input from flat entities (dataloader,
minimal-metadata, view controller, command-menu-item navigation context)
derive it via `belongsToTwentyStandardApp`; GraphQL resolvers keep
passing DTOs, which already carry the derived value.

## Testing

- Unit tests for both resolvers, including a new regression test: a
custom label matching a standard catalog entry is returned verbatim,
Lingui never called.

---------

Co-authored-by: Weiko <corentin@twenty.com>

packages/twenty-server/src/engine/metadata-modules/minimal-metadata/minimal-metadata.service.ts

@@ -78,12 +78,15 @@ export class MinimalMetadataService {
       .filter(isDefined)
       .filter((flatObjectMetadata) => flatObjectMetadata.isActive === true)
       .map((flatObjectMetadata) => {
+        const isCustom = !belongsToTwentyStandardApp(flatObjectMetadata);
+
         const objectMetadataForOverride = {
           labelPlural: flatObjectMetadata.labelPlural,
           labelSingular: flatObjectMetadata.labelSingular,
           description: flatObjectMetadata.description ?? undefined,
           icon: flatObjectMetadata.icon ?? undefined,
           color: flatObjectMetadata.color ?? undefined,
+          isCustom,
           standardOverrides: flatObjectMetadata.standardOverrides ?? undefined,
         };
 
@@ -104,7 +107,7 @@ export class MinimalMetadataService {
             i18nInstance,
           ),
           icon: flatObjectMetadata.icon ?? undefined,
-          isCustom: !belongsToTwentyStandardApp(flatObjectMetadata),
+          isCustom,
           isActive: flatObjectMetadata.isActive,
           isSystem: flatObjectMetadata.isSystem,
           isRemote: flatObjectMetadata.isRemote,