feat: CnChatWidget — AI chat widget with RAG context

[rubenvdlinde]

Description

OpenRegister has a full chat/AI system (ChatController + ChatService) with multi-turn conversation, RAG retrieval, and function calling. No frontend widget exists.

Requirements

• Chat widget (collapsible panel or sidebar tab)
• Message history with user/assistant turns
• Context-aware: knows which object/schema user is viewing
• Streaming response support
• Feedback buttons (thumbs up/down per response)

Backend API

• POST /api/chat/messages — send message
• GET /api/chat/conversations — list conversations
• GET /api/chat/conversations/{id}/messages — message history

Priority

LOW — but high differentiator for AI-powered apps