feat: window size presets — 4x8 screen-ratio grid in settings (v1.8.0)

- Settings 'Size' section: 8 col x 4 row grid, 31 buttons labeled a:b
  (a splits H, b splits W); top-left cell empty placeholder (no 1:1 —
  title bar double click already maximizes)
- Click resizes the window to work.width/b x work.height/a of the
  display's work area (screen_retriever visibleSize, taskbar excluded);
  position unchanged, no selection state tracking
- minimumSize 400x300 -> 160x100 (4:8 cell needs it)
- Settings file-properties rows left-aligned (were centered under path)

lib/screens/viewer_screen.dart

@@ -13,11 +13,12 @@ import '../services/crop_save_service.dart';
 import '../widgets/custom_title_bar.dart';
 import '../widgets/image_canvas.dart';
 import '../widgets/window_resize_zones.dart';
+import '../widgets/window_size_selector.dart';
 import '../shortcuts/app_shortcuts.dart';
 import '../services/window_persistence.dart';
 import '../l10n/app_localizations.dart';
 
-const appVersion = '1.7.2';
+const appVersion = '1.8.0';
 
 class ViewerScreen extends StatefulWidget {
   final List<String> initialFiles;
@@ -137,6 +138,11 @@ class _ViewerScreenState extends State<ViewerScreen> with WindowListener {
                   },
                 ),
                 const Divider(color: Colors.white24, height: 24),
+                WindowSizeSelector(
+                  workArea: _workArea,
+                  onPick: _applyWindowSize,
+                ),
+                const Divider(color: Colors.white24, height: 24),
                 if (_hasImages) ...[
                   Text(AppLocalizations.of(context)!.fileProperties,
                       style: const TextStyle(color: Colors.white70, fontSize: 13)),
@@ -146,6 +152,7 @@ class _ViewerScreenState extends State<ViewerScreen> with WindowListener {
                     builder: (context, snap) {
                       if (!snap.hasData) return const SizedBox(height: 20);
                       return Column(
+                        crossAxisAlignment: CrossAxisAlignment.start,
                         children: snap.data!.map((r) => Padding(
                           padding: const EdgeInsets.only(bottom: 2),
                           child: Text.rich(
@@ -259,6 +266,19 @@ class _ViewerScreenState extends State<ViewerScreen> with WindowListener {
 
   void _flipHorizontal() => _canvasKey.currentState?.toggleFlipH();
 
+  Future<Size?> _workArea() async {
+    final pos = await windowManager.getPosition();
+    return WindowPersistence.workAreaSize(windowPosition: pos);
+  }
+
+  Future<void> _applyWindowSize(int rows, int cols, Size work) async {
+    try {
+      await windowManager.setSize(Size(work.width / cols, work.height / rows));
+    } catch (_) {
+      // Boyutlandırma başarısız olursa sessizce geç (buton saf eylem).
+    }
+  }
+
   Future<void> _cropSave() async {
     final path = ImageManager.instance.currentImagePath;
     final state = _canvasKey.currentState;