refactored data providers with centralized cache resolution, unified UI using custom dialogs and bottom sheets, and enhanced network error handling for Dio and TLS errors

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

@@ -3,14 +3,22 @@ const double kCalendarEndHour = 17.25;
 const Duration kCalendarTimeInterval = Duration(minutes: 30);
 const double kCalendarViewHeaderHeight = 60;
 
-/// Minimum pixels per hour. Below this, the grid scrolls vertically rather
-/// than compressing further.
+/// 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.
+/// The grid scrolls vertically once lessons would otherwise be smaller.
 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.
+/// Fixed (independent of actual break duration); breaks render as a compact
+/// indicator.
 const double kBreakBlockHeight = 28;
+
+const int kOutsideChipsMaxVisible = 2;
+const double kOutsideChipHeight = 22;
+const double kOutsideChipSpacing = 3;
+const double kOutsideStripVerticalPadding = 3;
+
+const double kAppointmentTitleFontSize = 15;
+const double kAppointmentTitleMinFontSize = 11;
+const double kAppointmentBodyFontSize = 10;
+const double kAppointmentBodyLineHeight = 1.15;