The LINE adapter classified every non-text inbound message as
`MessageType.IMAGE`, which doesn't exist on the enum — so any image,
video, audio, file, sticker, or location message raised AttributeError
the moment it was constructed.
Beyond fixing the crash, every non-text message was being collapsed onto
a single type. The gateway routes on MessageType (voice → STT, files →
document handling, etc.), so misclassification silently mishandled media.
Replace the inline ternary with a `_LINE_MESSAGE_TYPES` lookup that maps
each LINE webhook type to its proper enum member (audio → VOICE to match
how Telegram/WhatsApp treat voice notes), falling back to TEXT for
unknown types. Adds regression tests covering the mapping and the old
AttributeError.
Co-authored-by: Sahibzada Allahyar <94376830+sahibzada-allahyar@users.noreply.github.com>
7309f3bef7