* feat: Implement existing template linking for CSAT surveys
- Added functionality to link existing CSAT templates for WhatsApp channels.
- Introduced a new component for selecting existing templates.
- Updated the dashboard settings page to support template mode switching between creating new and using existing templates.
- Enhanced the CSAT template management service to handle linking existing templates and fetching available templates.
- Updated API routes to include linking and fetching available templates.
- Added tests for the new linking functionality and template availability checks.
* feat: Enhance CSAT template handling and validation across services and components
* feat: Refactor body variable extraction for CSAT templates and update related validations
* feat: Add linked_at field to CSAT template responses and update related handling
* feat: Add tests for ConversationDrop date formatting and CSAT template body variable handling
# Pull Request Template
## Description
This PR introduces basic customization options for the CSAT survey:
* **Display Type**: Option to use star ratings instead of emojis.
* **Message Text**: Customize the survey message (up to 200 characters).
* **Survey Rules**: Send surveys based on labels — trigger when a
conversation has or doesn't have a specific label.
Fixes
https://linear.app/chatwoot/document/improve-csat-responses-a61cf30e054e
## Type of change
- [x] New feature (non-breaking change which adds functionality)
## How Has This Been Tested?
### Loom videos
**Website Channel (Widget)**
https://www.loom.com/share/7f47836cde7940ae9d17b7997d060a18?sid=aad2ad0a-140a-4a09-8829-e01fa2e102c5
**Email Channel (Survey link)**
https://www.loom.com/share/e92f4c4c0f73417ba300a25885e093ce?sid=4bb006f0-1c2a-4352-a232-8bf684e3d757
## 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
- [ ] Any dependent changes have been merged and published in downstream
modules
---------
Co-authored-by: Pranav <pranavrajs@gmail.com>
