feat: Backend - Companies API endpoint with pagination and search (#12840)

## Description

Adds API endpoint to list companies with pagination, search, and
sorting.

Fixes
https://linear.app/chatwoot/issue/CW-5930/add-backend-routes-to-get-companies-result
Parent issue:
https://linear.app/chatwoot/issue/CW-5928/add-companies-tab-to-dashboard

## Type of change

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

## How Has This Been Tested?

Added comprehensive specs to
`spec/enterprise/controllers/api/v1/accounts/companies_controller_spec.rb`:
- Pagination (25 per page, multiple pages)
- Search by name and domain (case-insensitive)
- Counter cache for contacts_count
- Account scoping
- Authorization

To reproduce:
```bash
bundle exec rspec spec/enterprise/controllers/api/v1/accounts/companies_controller_spec.rb
bundle exec rubocop enterprise/app/controllers/api/v1/accounts/companies_controller.rb
```

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] 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
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>
Co-authored-by: Sojan Jose <sojan@pepalo.com>

enterprise/app/controllers/api/v1/accounts/companies_controller.rb

@@ -1,9 +1,29 @@
 class Api::V1::Accounts::CompaniesController < Api::V1::Accounts::EnterpriseAccountsController
+  include Sift
+  sort_on :name, type: :string
+  sort_on :domain, type: :string
+  sort_on :created_at, type: :datetime
+
+  RESULTS_PER_PAGE = 25
+
   before_action :check_authorization
+  before_action :set_current_page, only: [:index, :search]
   before_action :fetch_company, only: [:show, :update, :destroy]
 
   def index
-    @companies = Current.account.companies.ordered_by_name
+    @companies = fetch_companies(resolved_companies)
+    @companies_count = @companies.total_count
+  end
+
+  def search
+    if params[:q].blank?
+      return render json: { error: I18n.t('errors.companies.search.query_missing') },
+                    status: :unprocessable_entity
+    end
+
+    companies = resolved_companies.search_by_name_or_domain(params[:q])
+    @companies = fetch_companies(companies)
+    @companies_count = @companies.total_count
   end
 
   def show; end
@@ -24,6 +44,20 @@ class Api::V1::Accounts::CompaniesController < Api::V1::Accounts::EnterpriseAcco
 
   private
 
+  def resolved_companies
+    @resolved_companies ||= Current.account.companies
+  end
+
+  def set_current_page
+    @current_page = params[:page] || 1
+  end
+
+  def fetch_companies(companies)
+    filtrate(companies)
+      .page(@current_page)
+      .per(RESULTS_PER_PAGE)
+  end
+
   def check_authorization
     raise Pundit::NotAuthorizedError unless ChatwootApp.enterprise?