fix: right-button double click no longer wipes rotation mid-drag (v1.7.2)

Two rotate drags started quickly at nearly the same spot were treated as a
double click: the reset was detected on button down against the previous down
time/position, so it wiped all effects and ignored the second drag, leaving
Ctrl+S to save an unrotated crop.

- Double click is now only counted for actual clicks (movement <= 4px) and is
  decided on button up; a drag breaks the chain.
- Pointer up is matched by pointer id, so a left-drag pan never counts as a click.
- dist: 1.7.2 .deb replaces the tracked 1.7.1 package.

lib/screens/viewer_screen.dart

@@ -17,7 +17,7 @@ import '../shortcuts/app_shortcuts.dart';
 import '../services/window_persistence.dart';
 import '../l10n/app_localizations.dart';
 
-const appVersion = '1.7.1';
+const appVersion = '1.7.2';
 
 class ViewerScreen extends StatefulWidget {
   final List<String> initialFiles;