Frontend Improvements: Named Conversations, Streaming, and Error/Empty State #22
Description
Upgrade frontend UX:
- Conversation title is generated after first LLM response and saved into session.metadata["title"]
- Conversation sidebar: show all sessions with title + timestamp, allow rename/delete
- Message streaming: /api/chat returns as SSE/StreamingResponse (word-by-word)
- Empty state: show suggested questions (config list) on new session
- Surface API errors in the UI