Upgrade Typing Game, Chat Backend, and Main Index Files

[TacticalReader]

This PR includes:

Enhanced typing game UI and functionality (4-typing-game/solution/index.*).

Upgraded chat backend files with optimized APIs and logic (9-chat-project/solution/backend/python/api.py, llm.py).

Improved main index presentation (index.css, index.html).

Total changes: 804 insertions, 221 deletions across 14 files.

Includes bug fixes, code clean-up, and feature improvements. Kindly review and merge