fix: title bar inceltildi (28px), degrade kaldırıldı

lib/screens/viewer_screen.dart

@@ -119,7 +119,7 @@ class _ViewerScreenState extends State<ViewerScreen> with WindowListener {
             child: Stack(
               children: [
                 Positioned(
-                  top: 40,
+                  top: 28,
                   left: 0,
                   right: 0,
                   bottom: 0,

lib/widgets/custom_title_bar.dart

@@ -12,24 +12,9 @@ class CustomTitleBar extends StatelessWidget {
       right: 0,
       child: DragToMoveArea(
         child: SizedBox(
-          height: 40,
+          height: 28,
           child: Stack(
             children: [
-              // Çok hafif degrade — masaüstü arka planı hafifçe karartır
-              Positioned.fill(
-                child: Container(
-                  decoration: const BoxDecoration(
-                    gradient: LinearGradient(
-                      begin: Alignment.topCenter,
-                      end: Alignment.bottomCenter,
-                      colors: [
-                        Color.fromRGBO(0, 0, 0, 0.1),
-                        Color.fromRGBO(0, 0, 0, 0.0),
-                      ],
-                    ),
-                  ),
-                ),
-              ),
               Positioned(
                 right: 0,
                 top: 0,
@@ -69,9 +54,9 @@ class _BarButton extends StatelessWidget {
       child: MouseRegion(
         cursor: SystemMouseCursors.click,
         child: SizedBox(
-          width: 44,
-          height: 40,
-          child: Icon(icon, color: Colors.white54, size: 18),
+          width: 36,
+          height: 28,
+          child: Icon(icon, color: Colors.white54, size: 16),
         ),
       ),
     );