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/installation_config.rb

@@ -24,6 +24,8 @@ class InstallationConfig < ApplicationRecord
   before_validation :set_lock
   validates :name, presence: true
 
+  # TODO: Get rid of default scope
+  # https://stackoverflow.com/a/1834250/939299
   default_scope { order(created_at: :desc) }
   scope :editable, -> { where(locked: false) }