fix: Filter out unsupported ephemeral message attachments (#13003)

Fixes
https://linear.app/chatwoot/issue/CW-6070/argumenterror-ephemeral-is-not-a-valid-file-type-argumenterror

**Problem**
The instagram webhooks containing ephemeral (disappearing) message were
causing ArgumentError exceptions because this attachment type is not
supported and was not in the enum validation.

**Solution**
- Added ephemeral to the unsupported_file_type? filter
- Ephemeral attachments are now silently filtered out before processing,
following the same pattern as existing unsupported types (template,
unsupported_type)

app/builders/messages/messenger/message_builder.rb

@@ -101,6 +101,6 @@ class Messages::Messenger::MessageBuilder
   private
 
   def unsupported_file_type?(attachment_type)
-    [:template, :unsupported_type].include? attachment_type.to_sym
+    [:template, :unsupported_type, :ephemeral].include? attachment_type.to_sym
   end
 end