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/components-next/template-preview/CallToActionTemplate.vue

@@ -0,0 +1,33 @@
+<script setup>
+import Button from 'dashboard/components-next/button/Button.vue';
+
+defineProps({
+  message: {
+    type: Object,
+    required: true,
+  },
+});
+</script>
+
+<template>
+  <div class="flex flex-col gap-2.5 text-n-slate-12 max-w-80">
+    <div class="p-3 rounded-xl bg-n-alpha-2">
+      <span
+        v-dompurify-html="message.content"
+        class="text-sm font-medium prose prose-bubble"
+      />
+    </div>
+    <div
+      v-if="message.buttons && message.buttons.length > 0"
+      class="flex flex-col gap-2"
+    >
+      <Button
+        v-for="(button, index) in message.buttons"
+        :key="index"
+        :label="button.text || button.title || 'Button'"
+        slate
+        class="!text-n-blue-11 w-full"
+      />
+    </div>
+  </div>
+</template>