feat: relocate import tools into studio and harden catalog/furnidata integrity

- Move /admin/import/* tools under /admin/studio/* and add studio nav, layout and tabs
- Add shared catalog maintenance panel plus a /admin/studio/maintenance tab
- Make furnidata reconciliation overwrite conflicting entries with the
  DB-authoritative items_base classname/id (surfaced via fixedConflicts)
- Add furnidata_translate_enabled setting to skip the heavy localized
  furnidata build during import (manual build-languages still forces it)
- Update staff smoke contract test for the studio hub

src/app/api/admin/import/furni/route.ts

@@ -220,7 +220,7 @@ export const GET = withAdmin(
 		}
 
 		if (action === "build-languages") {
-			const languages = await buildLocalizedFurniDataFiles();
+			const languages = await buildLocalizedFurniDataFiles(true);
 			return apiOk({ languages });
 		}
 
@@ -680,6 +680,7 @@ export const POST = withAdmin(
 			furniDataFixedIds: furniReconcile.fixedIds,
 			furniDataFixedOfferIds: furniReconcile.fixedOfferIds,
 			furniDataMissing: furniReconcile.missing,
+			furniDataFixedConflicts: furniReconcile.fixedConflicts,
 			furniDataConflicts: furniReconcile.conflicts,
 			offerRebuildChecked: offerRebuild.checked,
 			offerRebuildFixed: offerRebuild.fixed,