باسم الله، والحمد لله والصلاة والسلام على رسول الله

Wa 'alaykum salam.

May Allah reward you for your question.

In summary, if the application is merely an administrative tool, and it would be if:

1. No money is borrowed
2. No debt is created
3. No legal obligation to repay with interest exists
4. The application is only used as a means-testing gateway
5. And you are not considered a borrower from the perspective of Islamic Law.

Then this is permissible, because:

1. Ribā is not actually entered into
2. No sinful contract is concluded
3. The intent and reality are both free of ribā

However, if the application legally binds you to a loan contract, and this would be the case if:

1. The agreement includes binding clauses referring to interest
2. You are legally classed as having entered a loan agreement
3. Interest applies automatically if the amount changes later
4. You are signing something that would become ribā-based if activated;

Then this is not permissible, even if the amount is £0, because:

1. You have consented to a ribā framework
2. The prohibition applies to the contract itself, not the amount

And Allah knows best.