feat: implement Open-Meteo weather service

[hasanmo]

Issue 5 – Implement weatherService

Change

The application needed a single place for retrieving and converting weather data. React components should not need to understand the original Open-Meteo response format.

This change adds a weatherService that:

• fetches current weather data from Open-Meteo
• uses city coordinates to build the request
• checks the HTTP response
• converts the API response to the project's WeatherData type
• throws an error when the request fails
• does not cache or persist weather data

React components can now retrieve weather data using:

const weather = await getWeather(city);

Closes #6

[oliveror]

Over all, the PR seems good to me, but I have added a couple suggestions for more accurate documentation.