Replace Selenium with Direct HTTP Requests

[KaykCaputo]

Description:

The project currently uses Selenium WebDriver to fetch data from URLs such as:
https://sisu-api.sisu.mec.gov.br/api/v1/oferta/instituicoes/uf
https://sisu-api.sisu.mec.gov.br/api/v1/oferta/instituicao/{iesCode}
https://sisu-api.sisu.mec.gov.br/api/v1/oferta/{offerCode}/modalidades

These endpoints return raw JSON, so using Selenium to load a browser, parse HTML, and extract the JSON from a <pre> tag is unnecessary. This makes the program slower, more fragile, and more resource-heavy.
This issue proposes replacing all Selenium-based HTTP fetching with direct HttpClient GET requests.

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Tasks

• Create a static HttpClient instance, e.g.:
  private static readonly HttpClient client = new HttpClient();
• Replace all driver.Navigate().GoToUrl(url) calls with:
  var json = await client.GetStringAsync(url);
• Remove HTML parsing using HtmlAgilityPack
• Deserialize JSON directly using JsonConvert.DeserializeObject
• Preserve existing data structures (Institution, Course, CourseWeights, etc.)
• Remove Selenium and HtmlAgilityPack from the project dependencies
• Update README to reflect that Selenium is no longer required
• Ensure all current features behave identically after the change

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Why This Is Good for Beginners

• Involves simple and clear modifications
• Improves code performance and maintainability
• No advanced browser automation required
• Easy to test because the APIs are public and return consistent JSON
• Gives contributors experience with networking and JSON parsing

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Optional Enhancements

• Add error handling for network failures
• Implement timeout for requests
• Validate missing or malformed JSON fields