fix: Prevent unsupported file types on clipboard paste (#13182)

# Pull Request Template

## Description

This PR adds file type validation for clipboard-pasted attachments and
prevents unsupported file types from being attached across channels.

https://developers.chatwoot.com/self-hosted/supported-features#outgoing-attachments-supported-file-types

Fixes
https://linear.app/chatwoot/issue/CW-6233/bug-unsupported-file-types-allowed-via-clipboard-paste

## Type of change

- [x] Bug fix (non-breaking change which fixes an issue)

## How Has This Been Tested?

**Loom video**

**Before**
https://www.loom.com/share/882c335be4894d86b9e149d9f7560e72

**After**
https://www.loom.com/share/90ad9605fc4446afb94a5b8bbe48f7db


## 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: Muhsin Keloth <muhsinkeramam@gmail.com>

app/javascript/dashboard/components/widgets/conversation/ReplyBox.vue

@@ -45,6 +45,7 @@ import {
   removeSignature,
   getEffectiveChannelType,
 } from 'dashboard/helper/editorHelper';
+import { isFileTypeAllowedForChannel } from 'shared/helpers/FileHelper';
 
 import { LOCAL_STORAGE_KEYS } from 'dashboard/constants/localStorage';
 import { LocalStorage } from 'shared/helpers/localStorage';
@@ -637,6 +638,25 @@ export default {
       // Filter valid files (non-zero size)
       Array.from(e.clipboardData.files)
         .filter(file => file.size > 0)
+        .filter(file => {
+          const isAllowed = isFileTypeAllowedForChannel(file, {
+            channelType: this.channelType || this.inbox?.channel_type,
+            medium: this.inbox?.medium,
+            conversationType: this.conversationType,
+            isInstagramChannel: this.isAnInstagramChannel,
+            isOnPrivateNote: this.isOnPrivateNote,
+          });
+
+          if (!isAllowed) {
+            useAlert(
+              this.$t('CONVERSATION.FILE_TYPE_NOT_SUPPORTED', {
+                fileName: file.name,
+              })
+            );
+          }
+
+          return isAllowed;
+        })
         .forEach(file => {
           const { name, type, size } = file;
           this.onFileUpload({ name, type, size, file });