feat: jfif/jpe/wbmp format destegi, pencere cascade yerlesimi, konum kaydi duzeltmesi

- file_handler/image_manager: jfif, jpe, wbmp uzantilari
- .desktop + install.sh MimeType: image/vnd.wap.wbmp eklendi
- main.dart: yeni pencere oncekinin saginda acilir (screen_retriever ile ekran tespiti)
- viewer_screen: 2sn polling kaldirildi, konum kaydi tek akisa oturtuldu (acilis + move/resize debounce + close senkron)
- dist/rebuild-deb.sh: .desktop kaynaktan kopyalanir (MimeType/StartupWMClass guncel kalir)
- .deb guncellendi, docs: session-2026-08-03 + plan dokumanlari

lib/screens/viewer_screen.dart

@@ -21,7 +21,6 @@ class _ViewerScreenState extends State<ViewerScreen> with WindowListener {
   bool _hasImages = false;
   bool _isDragging = false;
   Timer? _saveDebounce;
-  Timer? _pollTimer;
   Rect _lastBounds = Rect.zero;
 
   @override
@@ -35,29 +34,6 @@ class _ViewerScreenState extends State<ViewerScreen> with WindowListener {
         FileHandler.loadImagesFromPaths(widget.initialFiles);
       });
     }
-
-    // İlk kayıt + periyodik polling başlat
-    WidgetsBinding.instance.addPostFrameCallback((_) async {
-      await Future.delayed(const Duration(milliseconds: 200));
-      await _doSave();
-      _startPolling();
-    });
-  }
-
-  void _startPolling() {
-    _pollTimer?.cancel();
-    _pollTimer = Timer.periodic(const Duration(seconds: 2), (_) async {
-      try {
-        final bounds = await windowManager.getBounds();
-        if (bounds != _lastBounds) {
-          _lastBounds = bounds;
-          WindowPersistence.saveSync(
-            position: bounds.topLeft,
-            size: bounds.size,
-          );
-        }
-      } catch (_) {}
-    });
   }
 
   @override
@@ -65,7 +41,6 @@ class _ViewerScreenState extends State<ViewerScreen> with WindowListener {
     windowManager.removeListener(this);
     ImageManager.instance.removeListener(_onImageManagerChanged);
     _saveDebounce?.cancel();
-    _pollTimer?.cancel();
     super.dispose();
   }
 
@@ -74,10 +49,18 @@ class _ViewerScreenState extends State<ViewerScreen> with WindowListener {
   void onWindowEvent(String eventName) {
     switch (eventName) {
       case 'close':
-        _doSave();
+        // Senkron kayıt — async çağrı kapanışta tamamlanmayabilir
+        if (_lastBounds != Rect.zero) {
+          WindowPersistence.saveSync(
+            position: _lastBounds.topLeft,
+            size: _lastBounds.size,
+          );
+        }
         break;
       case 'resize':
       case 'move':
+        // Son bilinen konumu hemen güncelle (kapanış senkron kaydı için)
+        windowManager.getBounds().then((b) => _lastBounds = b).catchError((_) {});
         _saveDebounce?.cancel();
         _saveDebounce = Timer(const Duration(milliseconds: 300), () {
           _doSave();