feat: implement real-time exchange rates service with multi-source integration, caching, historical data, alerts, WebSocket, and background jobs

[OthmanImam]

Real-Time Exchange Rates Service

This PR introduces a comprehensive exchange rates service for supported cryptocurrencies and fiat currencies, featuring:

• Multi-source integration: Fetches rates from CoinGecko and CoinMarketCap with automatic failover.
• Real-time updates: WebSocket server (/ws/rates) broadcasts current and updated rates to clients.
• Historical data storage: Periodic background jobs store historical rates in Redis for analytics and reference.
• Price alert system: Users can set price alerts via API, with validation and storage.
• Caching and rate limiting: Redis caching for efficient data retrieval and API rate limit handling.
• Volatility calculations: Utility for price volatility analytics.
• Data validation and sanitization: Ensures safe and correct data throughout the service.
• API endpoints:
  • GET /api/rates/current — Get current exchange rates
  • GET /api/rates/historical — Get historical rates
  • POST /api/rates/alerts — Set price alerts
  • GET /api/rates/supported-currencies — List supported currencies

---

Close: #11

[Pvsaint]

@OthmanImam One check is failing, please fix

[OthmanImam]

Hi @Pvsaint
i have fixed it, thanks

[Pvsaint]

Looks okay!