custom login implementation, period-based timetable layout with overlap handling, enhanced error dialogs, and unified bottom sheets

lib/view/pages/timetable/data/calendar_layout.dart

@@ -6,3 +6,11 @@ const double kCalendarViewHeaderHeight = 60;
 /// Minimum pixels per hour. Below this, the grid scrolls vertically rather
 /// than compressing further.
 const double kCalendarMinPxPerHour = 56;
+
+/// Minimum height of a lesson block in the period-based layout. The grid
+/// scrolls vertically once lessons would otherwise be smaller than this.
+const double kLessonBlockMinHeight = 50;
+
+/// Fixed height of a break block in the period-based layout. Independent of
+/// the actual break duration; breaks are rendered as a compact indicator.
+const double kBreakBlockHeight = 28;