feat: migrations for document auto-sync [AI-141] (#14041)

# Pull Request Template

## Description

Add migrations for document auto-sync

Fixes # (issue)

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## How Has This Been Tested?
locally

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

db/migrate/20260410092751_add_edited_to_captain_assistant_responses.rb

@@ -0,0 +1,5 @@
+class AddEditedToCaptainAssistantResponses < ActiveRecord::Migration[7.0]
+  def change
+    add_column :captain_assistant_responses, :edited, :boolean, default: false, null: false
+  end
+end

db/migrate/20260410092752_add_sync_columns_to_captain_documents.rb

@@ -0,0 +1,11 @@
+class AddSyncColumnsToCaptainDocuments < ActiveRecord::Migration[7.0]
+  def change
+    change_table :captain_documents, bulk: true do |t|
+      t.integer :sync_status
+      t.datetime :last_synced_at
+      t.datetime :last_sync_attempted_at
+    end
+
+    add_index :captain_documents, [:account_id, :sync_status]
+  end
+end

db/migrate/20260410092753_backfill_edited_on_captain_assistant_responses.rb

@@ -0,0 +1,20 @@
+class BackfillEditedOnCaptainAssistantResponses < ActiveRecord::Migration[7.0]
+  def up
+    return unless ChatwootApp.enterprise?
+
+    # rubocop:disable Rails/SkipsModelValidations
+    # NOTE: Since there is no way of knowing currently which FAQs were edited by a human
+    # we use a heuristic based on time passed between created_at and updated_at.
+    # 15 days is arbitrary but seems reasonable for a user to go back and edit an FAQ.
+    Captain::AssistantResponse
+      .where('updated_at - created_at > make_interval(days := ?)', 15)
+      .in_batches(of: 1000) do |batch|
+        batch.update_all(edited: true)
+      end
+    # rubocop:enable Rails/SkipsModelValidations
+  end
+
+  def down
+    # no-op: rolling back migration of edited column will drop the edited column entirely
+  end
+end