Feature Suggestion: Add AI Conversation Memory

[sariyan-0]

I added session-based memory to the /chat route so the AI can remember the last 10 messages. This improves continuity and makes the assistant feel more natural, with no repeated intros and better multi-step replies.

Changes:

• Stored chat history in session['chat_history']
• Sent history to Gemini as part of message_chain
• Avoided role: "system" (not supported by Gemini Flash)
• Added /clear_chat_history route to reset memory

It would be great to see this officially added — happy to help with a PR!