Move logic out of the Nunjucks views

### What feature do you want to see added?

Move logic out of the Nunjucks views and into the TS route functions.

### Why do you want this feature? Does it solve a problem?

Some (e.g., results.njk) have a lot of logic, for example if statement and for loops. It's safer to include these in the TS routes.

### How should the feature be implemented?

Consider what logic can be reused to reduce duplication.

### Additional context (if applicable)

_No response_