feat: Weather Retrieval

[anonfedora]

Add Weather API feature

This PR adds a new weather endpoint to our Axum server that fetches current weather data for multiple cities concurrently.

Changes

• Added /weather endpoint to retrieve weather data for London, Tokyo, and New York
• Integrated with the WeatherAPI service using environment variables for API key configuration
• Implemented concurrent API requests using Tokio's join! macro for improved performance
• Added necessary dependencies: reqwest with JSON feature and serde for serialization
• Created a shared application state with HTTP client to be reused across requests

Implementation Details

• Created a new weather.rs module with the weather endpoint handler
• Added AppState struct to hold the HTTP client and API key
• Modified server setup to initialize and pass application state to routes
• Set up proper environment variable handling for base URL and API key

Note: Requires WEATHER_API_KEY environment variable to be set before running the server.