Created more tests

[kfmelen]

Summary

Expand test coverage for core user journeys and GraphQL behavior.

• Test login, account creation, validation and failed authentication.
• Test review creation and deletion, including count updates and logged-out behavior.
• Test filtering, sorting, pagination and loading additional results without duplicates.
• Test adding and removing favorites across pages.
• Add keyboard and mobile viewport checks for the filter menu.
• Use controlled fixtures and a disposable database for integration tests.

Validation

• 17 component tests passed.
• 16 API and end-to-end tests passed.

Closes #79

[martiasu]

Lgtm!