[IMPROVEMENT] Explore page Trending widget shows skeleton loading for empty data

[NateIsern]

Description

The Trending widget on the Explore page and in the RightBar shows skeleton loading placeholders (gray bars) when there are no trending topics. Instead of showing skeletons indefinitely, it should either:

1. Show an empty state message (e.g., "No trending topics yet")
2. Hide the widget entirely when empty

Steps to Reproduce

1. Navigate to /explore
2. Observe the "Trending" section at the top shows gray skeleton bars
3. The RightBar "Trending" widget also shows skeleton bars
4. These never resolve to content (because there are no trending topics)

Expected Behavior

When trending data is empty, show a clean empty state or hide the section rather than showing perpetual skeleton loading.

Actual Behavior

Skeleton loading bars display indefinitely, suggesting content is loading when it's actually empty.

Impact

• Severity: Low (UX polish)
• Components: TrendsWidget, Explore page