[compass_app] Standardize on Result factories rather than constructors (#2538)

From my review of the recipes PR in
https://github.com/flutter/website/pull/11444#pullrequestreview-2480423811.

compass_app/app/lib/data/repositories/auth/auth_repository_dev.dart

@@ -16,12 +16,12 @@ class AuthRepositoryDev extends AuthRepository {
     required String email,
     required String password,
   }) async {
-    return Result.ok(null);
+    return const Result.ok(null);
   }
 
   /// Logout is always successful in dev scenarios
   @override
   Future<Result<void>> logout() async {
-    return Result.ok(null);
+    return const Result.ok(null);
   }
 }