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/services/contacts/company_association_service.rb

@@ -3,12 +3,13 @@ class Contacts::CompanyAssociationService
     return nil if skip_association?(contact)
 
     company = find_or_create_company(contact)
-    # rubocop:disable Rails/SkipsModelValidations
-    # Intentionally using update_column here to:
-    # 1. Avoid triggering callbacks
-    # 2. Improve performance (We're only setting company_id, no need for validation)
-    contact.update_column(:company_id, company.id) if company
-    # rubocop:enable Rails/SkipsModelValidations
+    if company
+      # rubocop:disable Rails/SkipsModelValidations
+      # Using update_column and increment_counter to avoid triggering callbacks while maintaining counter cache
+      contact.update_column(:company_id, company.id)
+      Company.increment_counter(:contacts_count, company.id)
+      # rubocop:enable Rails/SkipsModelValidations
+    end
     company
   end