feat: Add rich template preview for WhatsApp & Twilio Templates (#13206)

This PR introduces a comprehensive, display-only template preview system
for both WhatsApp and Twilio templates rendering of all supported
template types.

This lays the foundation for rich template previews across:
- Template selection modals
- Campaign creation flows
- Message composer
- Message screen.

<img width="1818" height="2058" alt="template-preview"
src="https://github.com/user-attachments/assets/9833b28c-f824-4568-8f74-6da09ac61f62"
/>

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: iamsivin <iamsivin@gmail.com>
Co-authored-by: Muhsin <12408980+muhsin-k@users.noreply.github.com>

app/javascript/dashboard/store/modules/specs/inboxes/templateFixtures.js

@@ -368,7 +368,7 @@ export const templates = [
     namespace: 'ed41a221_133a_4558_a1d6_192960e3aee9',
     components: [
       {
-        text: '🎉 Special offer for you! Get {{discount_percentage}}% off your next purchase. Use the code below at checkout',
+        text: 'Special offer for you! Get {{discount_percentage}}% off your next purchase. Use the code below at checkout',
         type: 'BODY',
       },
       {
@@ -400,7 +400,7 @@ export const templates = [
           {
             text: 'Call Support',
             type: 'PHONE_NUMBER',
-            phone_number: '+16506677566',
+            phone_number: '+23232323',
           },
         ],
       },