FR-2: Image Retrieval

• The relay must retrieve the actual image bytes from BlueBubbles
• BlueBubbles may expose attachments via:
  • Download URLs (if served over HTTP)
  • File paths on the Mac filesystem
  • Base64-encoded data in the API response
• The relay must handle all three formats and normalize to raw bytes before sending to the vision API
• The relay must validate that the retrieved data is a valid image (check magic bytes: JPEG FF D8, PNG 89 50, etc.)
• If retrieval fails, return an error state to the client