feat: add stock indicators route and Alpaca account info

- New /stocks route with StockViewer component
- New /api/indicators endpoint with SMA, EMA, RSI, MACD
- New /api/alpaca/account endpoint
- AlpacaAccountInfo component on home page
- Indicator calculation utilities
- Tests for utilities and components
- Vite proxy config for /api

app/routes/stocks.tsx

@@ -0,0 +1,9 @@
+import StockViewer from "../components/StockViewer";
+
+export default function Stocks() {
+  return (
+    <main className="flex items-start justify-center pt-8 pb-4">
+      <StockViewer />
+    </main>
+  );
+}