Simplify regex in Pagination test by using character class instead of alternation

### Description

There is a small regex simplification opportunity in the pagination tests.

In `frontend/.../Pagination.test.tsx`, the following regular expression is used:

/Go to page (1|2)$/

Since this pattern only matches single characters, the alternation can be simplified using a character class for better readability and consistency.

### Suggested Change

Replace:

/Go to page (1|2)$/

With:

/Go to page [12]$/

### Reason

- Improves readability
- Avoids unnecessary alternation
- Aligns with common regex best practices used elsewhere in the codebase

### Scope

This change only affects test code and does not alter application behavior.

### Reference

[SonarCloud](https://sonarcloud.io/project/issues?impactSeverities=MEDIUM&issueStatuses=OPEN%2CCONFIRMED&id=OWASP_Nest&open=AZhjQVNGifmo5YfJJ5vW)

Open frontend/.../Pagination.test.tsx and locate the pagination test using /Go to page (1|2)$/. Replace that pattern with /Go to page [12]$/ and verify the Pagination tests still pass with the same matching behavior.

Written by the indexing model from the issue text.