REST API — Media

1. POST /v1/media/presign     → upload_url, key, storage_filename
2. PUT  <upload_url>          → raw file bytes (no API key)
3. POST /v1/media/confirm     → media id

POST /v1/media/presign
Content-Type: application/json

{
  "filename": "photo.jpg",
  "content_type": "image/jpeg",
  "size_bytes": 1048576
}

curl -X PUT "$upload_url" \
  -H "Content-Type: image/jpeg" \
  --data-binary @photo.jpg

POST /v1/media/confirm
Content-Type: application/json

{
  "key": "uploads/.../uuid.jpg",
  "storage_filename": "uuid.jpg",
  "original_filename": "photo.jpg",
  "content_type": "image/jpeg",
  "size_bytes": 1048576
}