Conversation Flow and Reflection Updates

1. Updated the conversation flow: using matched kc for explanation and the lowest unexplored concept for question prompting.
2. Added the reflection popup window to show: a) the bullet point summarization of explored concepts, b) child feedback using a 4-point Likert scale
3. KCs are logged in the database
4. Split the response in the reflection stage into two part: a) question response (in the chat window) and b) conversation summarization (in the popup)
5. Fixed conversation stuck error