Add request/response compression support (gzip, deflate, brotli)

[tw4]

Summary

Nexar does not currently configure HTTP compression. This means responses are not automatically decompressed and the Accept-Encoding header is not sent, resulting in larger payloads and slower performance.

Problem

• No Accept-Encoding: gzip, deflate, br header is sent by default
• Compressed responses from servers are not automatically decompressed
• Increased bandwidth usage and slower response times

Proposed Solution

Configure the underlying HttpClientHandler to enable automatic decompression and optionally add compression support for request bodies.

var handler = new HttpClientHandler
{
    AutomaticDecompression = DecompressionMethods.GZip
                           | DecompressionMethods.Deflate
                           | DecompressionMethods.Brotli
};

Expose a configuration option in NexarConfig to enable/disable this behavior.