Refactor: Use Rails range syntax in ActivitySpike query (#2080)

Replace SQL string syntax with Rails range syntax for date filtering
in the ActivitySpike::Detector. This improves code readability and
follows Rails idioms.

Changed from:
  .where("created_at >= ?", recent_period.seconds.ago)

To:
  .where(created_at: recent_period.seconds.ago..)

This modernizes the codebase while maintaining the same functionality.

app/models/card/activity_spike/detector.rb

@@ -27,7 +27,7 @@ class Card::ActivitySpike::Detector
 
     def multiple_people_commented?(minimum_comments: 3, minimum_participants: 2)
       card.comments
-        .where("created_at >= ?", recent_period.seconds.ago)
+        .where(created_at: recent_period.seconds.ago..)
         .group(:card_id)
         .having("COUNT(*) >= ?", minimum_comments)
         .having("COUNT(DISTINCT creator_id) >= ?", minimum_participants)