Upload endpoint — POST /upload detects format, parses, stores conversation + messages

[Punkte]

What to build

A POST /upload route that accepts a conversation export file, auto-detects its format, runs the appropriate parser, and persists the conversation metadata and messages to the database. Returns the new conversation ID.

Acceptance criteria

• POST /upload accepts multipart file upload
• Format auto-detected from file content (WhatsApp .txt for now)
• Conversation row created with status = 'uploaded' then updated to 'ready'
• All parsed messages persisted (or in chunks — not necessarily individual rows)
• GET /conversations/:id returns conversation metadata and message count
• Returns { conversationId } on success with appropriate error responses

Blocked by

• WhatsApp parser — raw .txt export → ParsedConversation with unit tests #2