Market data provider

Source: src/utils/marketDataProvider.ts Singleton guard around Zerodha event processor lifecycle.

Functions

Function	Behavior
`initializeMarketData()`	Import and `zerodhaEvent.start()` once
`stopMarketData()`	`zerodhaEvent.stop()`, clear flag
`restartMarketData()`	Stop then initialize
`isMarketDataInitialized()`	Boolean guard

// POST /zerodha/start-market-data (from frontend Header)
await initializeMarketData();

// Post-login
await restartMarketData();

Currently hard-coded log message: provider: zerodha. Env DATA_PROVIDER=zerodha selects integration at app level.

Repeated initializeMarketData calls log warning and no-op if already running.