Skip AnalyzeJob when blob has no attachments

Upload-then-delete races cause AnalyzeJob to hit S3 after PurgeJob has
already removed the object, producing Aws::S3::Errors::NoSuchKey noise
in solid_queue_failed_executions. Since PurgeOnLastAttachment destroys
the attachment row before enqueueing PurgeJob, checking
blob.attachments.exists? catches this — a fast DB query that avoids the
S3 round-trip entirely.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/rails_ext/active_storage_analyze_job_suppress_broadcasts.rb

@@ -4,6 +4,8 @@
 # there is currently a bug https://github.com/rails/rails/issues/55144
 module ActiveStorageAnalyzeJobSuppressBroadcasts
   def perform(blob)
+    return unless blob.attachments.exists?
+
     Board.suppressing_turbo_broadcasts do
       Card.suppressing_turbo_broadcasts do
         super