Markets: table view with 24h price changes and chart links

[Copilot]

The markets page showed only current prices with no change data and no way to drill into charts. This adds 24h percentage changes, color-coded up/down indicators, and per-asset chart links.

Data layer (widgets/markets.go)

• New PriceData struct: { Price, Change24h }
• Crypto 24h changes fetched from CoinGecko (/api/v3/simple/price?include_24hr_change=true); cryptoGeckoIDs map translates tickers to CoinGecko IDs
• Futures/commodities use RegularMarketChangePercent already returned by finance-go (Yahoo Finance)
• New GetAllPriceData() function exposes enriched data; price_data.json persisted alongside prices.json

Page handler (markets/markets.go)

• Replaced card grid with a table: Symbol · Price · 24h Change · Chart
• chartLinks map routes crypto → CoinGecko, futures/commodities → Yahoo Finance
• formatChange() renders +5.00% / -2.34% with .markets-change-up / .markets-change-down / .markets-change-neutral CSS classes

Styles (app/html/mu.css)

• Added .markets-table, .markets-chart-link, and change color classes
• Responsive: reduced font/padding on mobile; chart column remains accessible

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