refactor: optimize AsyncFileResponse handling (#240)

* refactor: optimize AsyncFileResponse handling

This refactor improves AsyncFileResponse::AsyncFileResponse(File content, const String &path, const char *contentType, bool download, AwsTemplateProcessor callback)
The updated implementation:
- Replaces the use of String::endsWith() with a more efficient memcmp() check for gzip file suffix.
- Fix the download of precompresed archives. The old behavior was wrong.
- Simplifies content-disposition header generation using consistent logic for both inline and download cases.

Overall, the refactor enhances performance slightly and ensures more consistent behavior when serving compressed downloadable files.

* Add files via upload

* Update src/WebResponses.cpp

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/WebResponses.cpp

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Add files via upload

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Mathieu Carbou <mathieu.carbou@gmail.com>

Author: 3 people

src/WebResponses.cpp

@@ -758,7 +758,7 @@ AsyncFileResponse::AsyncFileResponse(File content, const String &path, const cha
   : AsyncAbstractResponse(callback) {
   _code = 200;
 
-  if (!download && String(content.name()).endsWith(T__gz) && !path.endsWith(T__gz)) {
+  if (String(content.name()).endsWith(T__gz) && !path.endsWith(T__gz)) {
     addHeader(T_Content_Encoding, T_gzip, false);
     _callback = nullptr;  // Unable to process gzipped templates
     _sendContentLength = true;