feat(prescription): enhance posology panel with horizontal scroll, arrows and calibrate print margins to 28pt

test/features/prescription_test.dart

@@ -103,6 +103,9 @@ void main() {
     });
 
     testWidgets('inserts sequential numbers and sub-indication dosis', (tester) async {
+      await tester.binding.setSurfaceSize(const Size(1024, 800));
+      addTearDown(() => tester.binding.setSurfaceSize(null));
+
       final configStore = ConfigStore();
       await tester.pumpWidget(
         MaterialApp(
@@ -134,6 +137,12 @@ void main() {
       await tester.pump();
       expect(find.text('1. \n2. \n   - '), findsOneWidget);
 
+      // Open posology panel
+      final posologyToggleBtn = find.text('⏱ Posologías rápidas ▼');
+      expect(posologyToggleBtn, findsOneWidget);
+      await tester.tap(posologyToggleBtn);
+      await tester.pump();
+
       // Tap quick dosage chip
       final chip = find.text('1 tableta');
       expect(chip, findsOneWidget);