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/types.ts

@@ -0,0 +1,15 @@
+export interface IndicatorData {
+  symbol: string;
+  indicators: {
+    sma: number;
+    ema: number;
+    rsi: number;
+    macd: number;
+  };
+}
+
+export interface AlpacaAccount {
+  cash: number;
+  buying_power: number;
+  portfolio_value: number;
+}