Fetch only relevant reviews

[tobiaheg]

Summary

Updates the existing reviews query to fetch only reviews for the selected game, instead of fetching all reviews and filtering them in the frontend.

• Requires gameId and filters reviews directly in the database.
• Returns reviews sorted newest first.
• Includes author names through a database join, removing the need to fetch all users.
• Removes frontend filtering, sorting, and user lookup.
• Fixes an existing unused prop binding in Top5Games that blocked the production build.

Validation

• Backend tests pass, including five review-related tests.
• All 19 frontend tests pass.
• Frontend production build passes.
• Database integration tests were not run because Docker access was unavailable.

No database migration is required.

Closes #84

[kfmelen]

LGTM!