Add caching layer for direct database queries

[chubes4]

Summary

Direct database queries should use WordPress caching mechanisms to improve performance.

Findings

• ~50+ warnings for uncached database calls
• Direct $wpdb->get_results() and similar calls without caching

Caching Options

1. Object Cache - wp_cache_get() / wp_cache_set()

   • Best for frequently accessed data
   • Persists across requests with object cache plugins

2. Transients - get_transient() / set_transient()

   • Best for data that can be stale temporarily
   • Built-in expiration support

Why This Matters

• Reduces database load
• Improves page load times
• Required for scalability on high-traffic sites
• Plugin Check requirement for performance

Acceptance Criteria

• Identify queries that benefit from caching
• Implement appropriate caching strategy for each
• Add cache invalidation on data changes
• Plugin Check passes caching validation