[Feature] Implement MyAssets route with stock data integration

[SrinidhiPerala2104]

Summary

Implement backend and frontend support for a "My Assets" feature that shows a user's portfolio with live stock prices.

Tasks

• Create myassets.py route to return portfolio data for a user
• Integrate get_price(symbol) in yftool to fetch current stock price
• Register myassets blueprint in __init__.py
• Update frontend (myasset.html + myasset.js) to load dynamic asset data
• Create and link pull request

Acceptance Criteria

• Visiting /myasset/<user_id> returns correct JSON
• Frontend correctly renders all user assets with live data