POST /api/cases lets the frontend actually create a new dava dosyası
(no working "Yeni Dosya" flow existed before). chatMessage now
generates a short title from a case's first message (like Claude/
ChatGPT auto-titling) and renames the case, returned as `newTitle`.
Chat panel's trash icon should remove the whole case (not just clear
its chat history) — documents/analyses/chat_messages cascade-delete
via the existing ON DELETE CASCADE foreign keys.
Frontend's chat history trash icon was calling this endpoint but it
didn't exist yet, causing a JSON-parse error on the default 404 page.
Also renames the LegalOS health-check message to AyrisLegal.
mstfyldz