feat: add missing fields to ResendBroadcast model (segment_id, html, text, topic_id)

[asielcabrera]

Description

The ResendBroadcast model is missing several fields returned by the API.

Missing Fields

Field	Type	Source
segmentId / segment_id	String?	GET /broadcasts/:id and list
html	String?	GET /broadcasts/:id
text	String?	GET /broadcasts/:id
topicId / topic_id	String?	GET /broadcasts/:id

Verification

Curl response from GET /broadcasts/:id:

{
  "id": "f6cfd6d3-...",
  "name": "Untitled",
  "audience_id": "44667bbd-...",
  "segment_id": "44667bbd-...",
  "html": "<p>Test</p>",
  "text": "Test",
  "topic_id": null,
  ...
}

Priority

Low — missing fields are silently ignored during decoding, so no breakage.