feat: Windows support - auto-update system + proper app icon

- PowerShell silent installer with UAC elevation
- Smart asset detection (x64 priority for .exe)
- Cross-platform restart after update
- Auto-check updates on launch (5 sec delay)
- Multi-layer .ico with 6 sizes (16-256px)
- Windows build documentation added

lib/features/app_update/data/github_release_parser.dart

@@ -23,7 +23,7 @@ abstract class GithubReleaseParser {
     }
     final preRelease = json["prerelease"] as bool;
     final publishedAt = DateTime.parse(json["published_at"] as String);
-    
+
     // Парсим assets
     final List<ReleaseAsset> assets = [];
     if (json["assets"] != null) {
@@ -36,7 +36,7 @@ abstract class GithubReleaseParser {
         ));
       }
     }
-    
+
     return RemoteVersionEntity(
       version: version,
       buildNumber: buildNumber,