feat: Companies page (#12842)

# Pull Request Template

## Description

This PR introduces a new Companies section in the Chatwoot dashboard. It
lists all companies associated with the account and includes features
such as **search**, **sorting**, and **pagination** to enable easier
navigation and efficient management.

Fixes
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?

### Screenshot
<img width="1619" height="1200" alt="image"
src="https://github.com/user-attachments/assets/21f0a666-c3d6-4dec-bd02-1e38e0cd9542"
/>



## 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
- [ ] 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: Vinay Keerthi <11478411+stonecharioteer@users.noreply.github.com>
Co-authored-by: Shivam Mishra <scm.mymail@gmail.com>

app/javascript/dashboard/featureFlags.js

@@ -41,6 +41,7 @@ export const FEATURE_FLAGS = {
   CAPTAIN_V2: 'captain_integration_v2',
   SAML: 'saml',
   QUOTED_EMAIL_REPLY: 'quoted_email_reply',
+  COMPANIES: 'companies',
 };
 
 export const PREMIUM_FEATURES = [