feat(open-webui): voice messages, fix camera capture and full notes

- Voice messages: record from the microphone and transcribe to the input
  via Open WebUI's /api/v1/audio/transcriptions (mic button in composer).
- Camera capture: attach the stream via a ref callback so the preview is
  no longer a black frame (the ref could be read before the video mounted).
- Notes: fetch the full note body on attach. The list endpoint truncates
  content to 1000 chars, so attached notes were cut off; getNote returns
  the complete markdown.

apps/docs/docs/widgets/open-webui/index.mdx

@@ -46,6 +46,7 @@ The AI Chat widget lets you chat with AI models served by Open WebUI directly fr
 | **Knowledge bases**     | Ground replies on any RAG knowledge collection your account owns, with an expandable picker to inspect a base's files.                     |
 | **Notes**               | Attach the contents of your Open WebUI notes.                                                                                              |
 | **Reference chats**     | Bring a previous conversation in as context for the current one.                                                                          |
+| **Voice messages**      | Record from your microphone and have Open WebUI transcribe it into the message box (requires STT configured in Open WebUI).                |
 
 ### Notes