fix(whatsapp): preserve and display flow responses (#15279)

WhatsApp Flow submissions currently reach Chatwoot as
`interactive.nfm_reply` messages, but their structured answers are
discarded. Agents see an empty message and outbound webhooks cannot
access the submitted data.

This change preserves the Flow response in message content attributes
and renders a readable response card in the conversation. Existing
WhatsApp messages and other interactive message types remain unchanged.

Fixes https://github.com/chatwoot/chatwoot/issues/13970


<img width="1234" height="1350" alt="CleanShot 2026-08-04 at 00 40
14@2x"
src="https://github.com/user-attachments/assets/884b3a5c-bab3-4196-8037-776e6c41ab2a"
/>


### How to reproduce

1. Send an approved WhatsApp template containing a Flow button.
2. Complete and submit the Flow from WhatsApp.
3. Open the conversation in Chatwoot.
4. Observe that the incoming message has no visible content and the
submitted fields are absent from the message webhook.

### What changed

- Parse `interactive.nfm_reply.response_json` for incoming WhatsApp
Cloud messages.
- Store the Flow name, body, and structured response under
`content_attributes.whatsapp_flow_response`.
- Add a dedicated conversation bubble that formats submitted field names
and values.
- Preserve original response keys while converting message attributes to
the frontend shape.
- Keep `flow_token` available in stored/webhook data while omitting it
from the agent-facing card.
- Add focused backend, helper, and component regression coverage.

### How to test

1. Send a WhatsApp Flow template to a contact.
2. Submit the Flow with multiple field types, including free text and a
selection.
3. Confirm the incoming conversation message displays each submitted
field and value.
4. Confirm an empty-answer Flow still renders a visible “Submitted a
flow response” message.
5. Inspect the `message_created` webhook and confirm the structured
response is present in
`content_attributes.whatsapp_flow_response.response_json`.

---------

Co-authored-by: Muhsin <12408980+muhsin-k@users.noreply.github.com>

config/locales/en.yml

@@ -302,6 +302,7 @@ en:
       whatsapp:
         list_button_label: 'Choose an item'
         call_permission_request_body: 'We would like to call you regarding your conversation.'
+        flow_response: 'Submitted a flow response'
         unsupported_message: 'This message is unavailable.'
       voice_call:
         twilio: 'Voice Call'