fix: stream attachment handling in workers (#12870)

We’ve been watching Sidekiq workers climb from ~600 MB at boot to
1.4–1.5 GB after an hour whenever attachment-heavy jobs run. This PR is
an experiment to curb that growth by streaming attachments instead of
loading the whole blob into Ruby: reply-mailer inline attachments,
Telegram uploads, and audio transcriptions now read/write in chunks. If
this keeps RSS stable in production we’ll keep it; otherwise we’ll roll
it back and keep digging

app/mailers/conversation_reply_mailer_attachment_helper.rb

@@ -0,0 +1,51 @@
+# Handles attachment processing for ConversationReplyMailer flows.
+module ConversationReplyMailerAttachmentHelper
+  private
+
+  def process_attachments_as_files_for_email_reply
+    # Attachment processing for direct email replies (when replying to a single message)
+    #
+    # How attachments are handled:
+    # 1. Total file size (<20MB): Added directly to the email as proper attachments
+    # 2. Total file size (>20MB): Added to @large_attachments to be displayed as links in the email
+
+    @options[:attachments] = []
+    @large_attachments = []
+    current_total_size = 0
+
+    @message.attachments.each do |attachment|
+      current_total_size = handle_attachment_inline(current_total_size, attachment)
+    end
+  end
+
+  def read_blob_content(blob)
+    buffer = +''
+    blob.open do |file|
+      while (chunk = file.read(64.kilobytes))
+        buffer << chunk
+      end
+    end
+    buffer
+  end
+
+  def handle_attachment_inline(current_total_size, attachment)
+    blob = attachment.file.blob
+    return current_total_size if blob.blank?
+
+    file_size = blob.byte_size
+    attachment_name = attachment.file.filename.to_s
+
+    if current_total_size + file_size <= 20.megabytes
+      content = read_blob_content(blob)
+      mail.attachments[attachment_name] = {
+        mime_type: attachment.file.content_type || 'application/octet-stream',
+        content: content
+      }
+      @options[:attachments] << { name: attachment_name }
+      current_total_size + file_size
+    else
+      @large_attachments << attachment
+      current_total_size
+    end
+  end
+end

app/mailers/conversation_reply_mailer_helper.rb

@@ -1,4 +1,6 @@
 module ConversationReplyMailerHelper
+  include ConversationReplyMailerAttachmentHelper
+
   def prepare_mail(cc_bcc_enabled)
     @options = {
       to: to_emails,
@@ -27,34 +29,6 @@ module ConversationReplyMailerHelper
     mail(@options)
   end
 
-  def process_attachments_as_files_for_email_reply
-    # Attachment processing for direct email replies (when replying to a single message)
-    #
-    # How attachments are handled:
-    # 1. Total file size (<20MB): Added directly to the email as proper attachments
-    # 2. Total file size (>20MB): Added to @large_attachments to be displayed as links in the email
-
-    @options[:attachments] = []
-    @large_attachments = []
-    current_total_size = 0
-
-    @message.attachments.each do |attachment|
-      raw_data = attachment.file.download
-      attachment_name = attachment.file.filename.to_s
-      file_size = raw_data.bytesize
-
-      # Attach files directly until we hit 20MB total
-      # After reaching 20MB, send remaining files as links
-      if current_total_size + file_size <= 20.megabytes
-        mail.attachments[attachment_name] = raw_data
-        @options[:attachments] << { name: attachment_name }
-        current_total_size += file_size
-      else
-        @large_attachments << attachment
-      end
-    end
-  end
-
   private
 
   def oauth_smtp_settings