[FE-53] Build paginated workspace reviews list component

[mftee]

Overview

Build a paginated reviews section component that displays workspace reviews with average rating breakdown. All work goes in frontend/sandbox/.

Acceptance Criteria

• Component at frontend/sandbox/components/ReviewsList.tsx
• Shows average rating as a large number with filled stars
• Rating breakdown bar chart (5 stars to 1 star with percentage bars)
• Individual review cards: reviewer name (masked), star rating, comment, date
• Pagination: load 5 reviews at a time with Load more button
• Sort options: Most Recent, Highest Rated, Lowest Rated
• Empty state when no reviews exist
• Demo page at frontend/sandbox/workspaces/[id]/page.tsx renders it below workspace details