Add automatic cleanup job for orphaned topic counters (total_projects_count)

Problem

Topics can show incorrect project counts when projects are deleted but ProjectTopic records remain orphaned, causing topic.total_projects_count to be out of sync.

Current Behavior

• Topic shows "X projects" in counter:

  

• Clicking on topic shows empty site:

  

  (potentially also fewer projects than counter indicates)

Validated discrepancy:

Expected Behavior

• Topic counters should accurately reflect the number of visible projects
• Automatic cleanup should handle orphaned ProjectTopic records

Proposed Solution

Add a scheduled cleanup job (similar to existing cleanup workers) that:

1. Identifies orphaned ProjectTopic records
2. Runs Projects::Topic.reset_counters for affected topics (topics where topic.total_projects_count != topic.projects.count )
3. Cleans up orphaned records

Related Code

• Projects::ProjectTopic model with counter_cache: :total_projects_count
• Similar pattern exists in Packages::Cleanup::DeleteOrphanedDependenciesWorker

Impact

• Improves data consistency
• Better user experience
• Reduces admin maintenance overhead