feat: Add attachment support for Signal and WhatsApp channels

- Signal: Use base64Attachments field in signal-cli-rest-api
- WhatsApp: Implement Baileys attachment sending for images, videos, audio, and documents
- Both channels retrieve attachments from Zammad Store model
- Support multiple attachments per message

packages/zammad-addon-bridge/src/lib/cdr_whatsapp_api.rb

@@ -35,6 +35,9 @@ class CdrWhatsappApi
   end
 
   def send_message(recipient, text, options = {})
-    post('send', { to: recipient.to_s, message: text }.merge(parse_hash(options)))
+    params = { to: recipient.to_s, message: text }
+    params[:attachments] = options[:attachments] if options[:attachments]
+    options.delete(:attachments) if options[:attachments]
+    post('send', params.merge(parse_hash(options)))
   end
 end