feat(extension): Enhanced HTTP API for YouTube Music support

- Add http.put(), http.delete(), http.patch() shortcut methods
- Add persistent cookie jar per extension
- Add http.clearCookies() to clear session
- Fix User-Agent header respect (no longer overwritten)
- Return multi-value headers as arrays (Set-Cookie support)
- Auto-stringify objects in POST/PUT/PATCH body
- Add response.ok and response.status properties
- Update documentation with YouTube Music example

lib/constants/app_info.dart

@@ -1,8 +1,8 @@
 /// App version and info constants
 /// Update version here only - all other files will reference this
 class AppInfo {
-  static const String version = '3.0.0-alpha.1';
-  static const String buildNumber = '50';
+  static const String version = '3.0.0-alpha.2';
+  static const String buildNumber = '51';
   static const String fullVersion = '$version+$buildNumber';