Fix: Optimize IMAP query and add timeout handling

Co-authored-by: pranavrajs <pranavrajs@gmail.com>

db/migrate/20250909000001_add_index_conversations_additional_attributes_in_reply_to.rb

@@ -0,0 +1,15 @@
+class AddIndexConversationsAdditionalAttributesInReplyTo < ActiveRecord::Migration[7.0]
+  disable_ddl_transaction!
+
+  def change
+    # Add GIN index for JSONB queries on conversations.additional_attributes->>'in_reply_to'
+    # This index will significantly improve the performance of the query:
+    # conversations.where("additional_attributes->>'in_reply_to' = ?", in_reply_to)
+    # which is used in ImapMailbox#find_conversation_by_in_reply_to
+    add_index :conversations, 
+              "((additional_attributes->>'in_reply_to'))", 
+              name: 'index_conversations_on_additional_attributes_in_reply_to',
+              algorithm: :concurrently,
+              where: "additional_attributes->>'in_reply_to' IS NOT NULL"
+  end
+end

spec/mailboxes/imap/imap_mailbox_spec.rb

@@ -264,5 +264,6 @@ RSpec.describe Imap::ImapMailbox do
         expect(conversation.additional_attributes['in_reply_to']).to eq(multiple_in_reply_to_mail.in_reply_to.first)
       end
     end
+
   end
 end