Webapp: Typing indicators, video, and message editing

Typing indicators, inline video, message editing, and a user info panel added to the webapp.

• Typing indicator with brand gradient animation, disappears cleanly when typing stops
• Edit sent messages in real time on both sides
• Paste a video link to embed it inline with auto-pause on scroll
• User info panel in the right sidebar: name, email, attributes, metadata
• Reduced re-renders and consistent loading states across the chat interface