fix: make sync endpoint market-aware — prevent US scan results from overwriting BIST file

fix: complete US market cleanup and smoke-test fixes

feat: full US market support across all pages and API routes

feat: live position monitoring with charts + trading system production ready

Production-ready: Eliminate toy data, enforce BUY gates, add API proxies

Use fetchJson wrapper across pages/components

Fix HF health check + remove hardcoded API base

Add missing API endpoints: stocks, movers, scanner, backtest, sentiment, news

Add Next.js app pages (portfolio, backtest, scanner)