fix: replace MD5 with SHA256

Author: Bulletdev

config/initializers/query_performance_monitoring.rb

@@ -69,7 +69,7 @@ def track_query_stats(payload, duration)
 
       # Normalize query for grouping (remove values)
       normalized = normalize_query(payload[:sql])
-      stats_key = "query_stats:#{Digest::MD5.hexdigest(normalized)}"
+      stats_key = "query_stats:#{Digest::SHA256.hexdigest(normalized)}"
 
       # Update counters and query info
       Rails.cache.redis.pipelined do |pipeline|