chore: Search optimisations (#6644)

- Strip search term before searching
- order messages by created_at desc
- order contacts by last_activity_at desc
- order conversations by created_at desc
- Search only resolved contacts
- Optimize resolved contacts query

ref: #6583

app/models/message.rb

@@ -81,6 +81,10 @@ class Message < ApplicationRecord
   scope :chat, -> { where.not(message_type: :activity).where(private: false) }
   scope :non_activity_messages, -> { where.not(message_type: :activity).reorder('id desc') }
   scope :today, -> { where("date_trunc('day', created_at) = ?", Date.current) }
+
+  # TODO: Get rid of default scope
+  # https://stackoverflow.com/a/1834250/939299
+  # if you want to change order, use `reorder`
   default_scope { order(created_at: :asc) }
 
   belongs_to :account